Patient specific implant technology

ABSTRACT

Patient specific implant technology, in which an outline representation of a portion of an outer surface of a periphery of a bone volume is determined and the outline representation is used in operations related to implant matching. In addition, an instrument may be made to match a perimeter shape of a Patient Specific Knee Implant with features for locating holes in a distal femur such that posts or lugs in a femoral implant locate the femoral implant centered medial-laterally within an acceptable degree of precision to prevent overhang of either the side of the femoral implant over the perimeter of the distal femur bone resections. Further, a two-dimensional outline representation may be segmented into segments that correspond to resection cuts used in fitting an implant on a portion of a bone and operations related to implant matching may be performed based on the segments.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Patent Application No.61/771,409, filed on Mar. 1, 2013, and U.S. Patent Application No.61/696,083, filed on Aug. 31, 2012. The disclosure of these priorapplications is incorporated by reference in its entirety.

FIELD

This disclosure relates to patient specific implant technology.

BACKGROUND

Implant (e.g., knee) systems have been sized based on medical imaging,cadaver dissection, and lessons learned from prior implant designs. Intypical implant surgery (e.g., Total Knee Arthroplasty (TKA)), bones arecut to fit implant dimensions. In TKA, femur bones are cut to fitimplants with an anterior cut, a distal chamfer cut, a distal cut, aposterior chamfer cut, and a posterior cut. In a resurfacing case, thebone cuts may be contoured to follow the original articular surfacecurvature or shape to some degree compared to the planar cuts inconventional TKA. Because a limited scope of implant sizes are availablein implant (e.g., knee) systems, compromises are made in placingimplants, such as allowing more resected bone to extend beyond theimplant perimeter or for the implant to overhang beyond the resectedbone. The mismatches between implant and bone may negatively impactpatient outcomes, potentially resulting in additional blood loss, softtissue risk, and post-operative pain.

SUMMARY

In one aspect, a system includes at least one processor and at least onecomputer-readable medium coupled to the at least one processor havingstored thereon instructions which, when executed by the at least oneprocessor, causes the at least one processor to perform operations. Theoperations include accessing a three-dimensional model of at least aportion of a bone, defining a three-dimensional solution volume based onresection cuts used in fitting an implant on the portion of the bone,and intersecting the three-dimensional model of the portion of the bonewith the three-dimensional solution volume to produce a resultant bonevolume represented in three dimensions. The operations also includedetermining an outline representation of at least a portion of an outersurface of a periphery of the resultant bone volume and using theoutline representation in one or more operations related to implantmatching.

Implementations may include one or more of the following features. Forexample, the operations may include accessing one or more images of theportion of the bone and generating the three-dimensional model of theportion of the bone based on the one or more images of the portion ofthe bone. The operations also may include defining a three-dimensionaltolerance volume based on one or more tolerances for one or morevariations related to an implant procedure for placing the implant onthe portion of the bone and intersecting the three-dimensional model ofthe portion of the bone with the three-dimensional tolerance volume toproduce the resultant bone volume represented in three dimensions. Theoperations further may include defining the three-dimensional tolerancevolume based on at least one of a tolerance related to variations insurgical technique in performing the implant procedure, a tolerancerelated to variations in medical instrumentation used in performing theimplant procedure, a tolerance related to variations in manufacturingthe implant used in the implant procedure, a tolerance related tovariations in anatomy of similar bones across patients, a tolerancerelated to variations in medical imaging used in generating thethree-dimensional model of the portion of the bone, and a tolerancerelated to variations in file conversion used in generating thethree-dimensional model of the portion of the bone

In some implementations, the operations may include identifying the oneor more tolerances for the one or more variations related to the implantprocedure, determining one or more measurements that account for the oneor more tolerances identified, and determining locations of resectioncuts used in fitting the implant on the portion of the bone. In theseimplementations, the operations may include defining thethree-dimensional tolerance volume based on the locations of theresection cuts and the one or more measurements that account for the oneor more tolerances identified.

In addition, the operations may include aligning the three-dimensionalsolution volume on a portion of the three-dimensional model of theportion of the bone using techniques designed to optimize placement ofan articular surface of the implant when placed on the portion of thebone. The operations may include evaluating the resultant bone volumewith respect to one or more rules related to placing the implant on theportion of the bone.

In some examples, the operations may include determining whether theresultant bone volume is sufficient for fitting the implant in a mannerthat provides sufficient contact with the implant and an acceptableposition of an articular surface of the implant. In these examples, theoperations may include maintaining the resultant bone volume withoutadjustment based on a determination that the resultant bone volume issufficient for fitting the implant in a manner that provides sufficientcontact with the implant and an acceptable position of an articularsurface of the implant. The determination of whether the resultant bonevolume is sufficient for fitting the implant may be a determination ofwhether the implant optimally fills the space left by the resected bone(e.g., fills the space within a threshold degree of closeness).

In some implementations, the operations may include adjusting theresultant bone volume based on the evaluation of the resultant bonevolume with respect to one or more rules related to placing the implanton the portion of the bone and determining an outline representation ofat least a portion of an outer surface of a periphery of the resultantbone volume after adjustment. In these implementations, the operationsmay include defining an acceptable zone based on a periphery of theimplant, intersecting the resultant bone volume with the acceptable zoneto produce an acceptable bone volume, and adjusting the resultant bonevolume based on the acceptable bone volume. Further, in theseimplementations, defining an implant tolerance zone based on sizing ofthe implant and one or more tolerances for one or more variationsrelated to an implant procedure for placing the implant on the portionof the bone, intersecting the resultant bone volume with the implanttolerance zone to produce an overlap bone volume, and adjusting theresultant bone volume based on the overlap bone volume.

In some examples, the operations may include defining an acceptable zonebased on a periphery of the implant and intersecting the resultant bonevolume with the acceptable zone to produce an acceptable bone volume. Inthese examples, the operations may include defining an implant tolerancezone based on sizing of the implant and one or more tolerances for oneor more variations related to an implant procedure for placing theimplant on the portion of the bone and intersecting the resultant bonevolume with the implant tolerance zone to produce an overlap bonevolume. Further, in these examples, the operations may include combiningthe acceptable bone volume with the overlap bone volume to produce acomposite bone volume and using the composite bone volume to generate anadjusted bone volume that defines inner and outer tolerance in threedimensions.

Also, the operations may include creating a bone surface ribbon from theouter surface of the periphery of the resultant bone volume and usingthe bone surface ribbon in one or more operations related to implantmatching. The operations may include fitting a curve to the bone surfaceribbon and using the curve fitted to the bone surface ribbon in one ormore operations related to implant matching. The operations further mayinclude designing a custom implant based on the outline representation.

In some implementations, the operations may include storing the outlinerepresentation in a database with sample outline representationsdetermined for other bone portions that correspond to the portion of thebone, analyzing characteristics of the outline representations stored inthe database, and, based on the analysis, clustering the outlinerepresentations stored in the database into multiple groups that eachincludes outline representations having similar characteristics. Inthese implementations, the operations may include defining an implantdesign for each of the multiple groups and, for each implant design,storing the implant design in association with one or more parametersthat enable matching of the implant design with patient bone data.

In some examples, the operations may include determining one or moreparameters of the outline representation, comparing the one or moreparameters of the outline representation to parameters associated withavailable implant designs, and, based on comparison results, determiningthat the one or more parameters of the outline representation match anavailable implant design within a threshold degree. In these examples,the operations may include outputting the available implant design asmatching the outline representation based on the determination that theone or more parameters of the outline representation match the availableimplant design within the threshold degree.

In some implementations, the operations may include determining one ormore parameters of the outline representation, comparing the one or moreparameters of the outline representation to parameters associated withavailable implant designs, and, based on comparison results, determiningthat the one or more parameters of the outline representation do notmatch an available implant design within a threshold degree. In theseimplementations, the operations may include, based on the determinationthat the one or more parameters of the outline representation do notmatch an available implant design within the threshold degree,determining that a custom implant is needed and outputting a messagethat indicates a custom implant is needed.

In another aspect, a method includes accessing a three-dimensional modelof at least a portion of a bone, defining a three-dimensional solutionvolume based on resection cuts used in fitting an implant on the portionof the bone, and intersecting the three-dimensional model of the portionof the bone with the three-dimensional solution volume to produce aresultant bone volume represented in three dimensions. The method alsoincludes determining, by at least one processor, an outlinerepresentation of at least a portion of an outer surface of a peripheryof the resultant bone volume and using the outline representation in oneor more operations related to implant matching.

In yet another aspect, at least one computer-readable storage medium isencoded with executable instructions that, when executed by at least oneprocessor, cause the at least one processor to perform operations. Theoperations include accessing a three-dimensional model of at least aportion of a bone, defining a three-dimensional solution volume based onresection cuts used in fitting an implant on the portion of the bone,and intersecting the three-dimensional model of the portion of the bonewith the three-dimensional solution volume to produce a resultant bonevolume represented in three dimensions. The operations also includedetermining an outline representation of at least a portion of an outersurface of a periphery of the resultant bone volume and using theoutline representation in one or more operations related to implantmatching.

In another aspect, an instrument for locating a medial-lateral positionof an implant includes a distal cut surface portion, an anterior chamferportion connected to the distal cut surface portion, and an anteriorflange portion connected to the anterior chamfer portion. The instrumentalso includes a posterior chamfer portion connected to the distal cutsurface portion, at least one paddle connected to the posterior chamferportion, and at least one locating hole in the distal cut surfaceportion. The distal cut surface portion has a lateral perimeter and amedial perimeter, and the lateral and medial perimeters each have apatient specific shape.

Implementations may include one or more of the following features. Forexample, the instrument may include a notch. The notch may be aposterior stabilizing box geometry. The posterior chamfer portion mayinclude a posterior lateral chamfer and a posterior medial chamfer. Theat least one paddle may include a posterior medial condyle and aposterior lateral condyle.

In addition, the instrument may include a patient specific implant witha perimeter, where at least the medial and lateral perimeters match aportion of the shape of the patient specific implant perimeter. Theinstrument also may include at least one pin hole. The least one pinhole may be circular.

Further, the least one locating hole may be circular. The least onelocating hole may be selected from a group consisting of holes, slots,overlapping holes, or combination slots that allow for variance in themedial-lateral and anterior-posterior directions. The instrument mayinclude a stiffener. The instrument may include articular surfaces.

In yet another aspect, an instrument for locating a medial-lateralposition of an implant on a distal portion of a femur that has anoverall width includes a distal cut surface portion having a maximumwidth, an anterior chamfer portion connected to the distal cut surfaceportion, and an anterior flange portion connected to the anteriorchamfer portion. The instrument also includes a posterior chamferportion connected to the distal cut surface potion, at least one paddleconnected to the posterior chamfer portion, and at least one locatinghole in the distal cut surface portion. The distal cut surface portionis centered relative to the overall width of the distal portion of thefemur.

In a further aspect, a method for locating an implant includes preparinga distal end of a femur, locating a maximum distal width of the distalend, and placing an instrument on the prepared femur. The instrumentincludes a distal cut surface portion, an anterior chamfer portionconnected to the distal cut surface portion, and an anterior flangeportion connected to the anterior chamfer portion. The instrument alsoincludes a posterior chamfer portion connected to the distal cut surfaceportion and at least one paddle connected to the posterior chamferportion. The method also includes moving the instrument in amedial-lateral direction to obtain equal perimeter offsets, pinning theinstrument, and creating at least one lug hole in the distal end of thefemur using the instrument.

Implementations may include one or more of the following features. Forexample, the step of creating at least one lug may use a drill, a reameror a punch. In addition, the method may include the steps of removingthe instrument and implanting a knee prosthesis.

In another aspect, a method for manufacturing an instrument may includeobtaining image data, generating a ribbon using the image data, andgenerating a spline using the ribbon. The method also includesgenerating offset distances for at least one lug location and importingthe spline into an instrument CAD model. The method further includesplacing the offset distances in the instrument CAD model and outputtingthe instrument CAD model to an electronic format suitable for rapidmanufacturing/additive manufacturing production equipment, such as a SLAfile.

The details of one or more implementations are set forth in theaccompanying drawings and the description, below. Other potentialfeatures of the disclosure will be apparent from the description anddrawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part ofthe specification, illustrate the embodiments of the present inventionand together with the written description serve to explain theprinciples, characteristics, and features of the invention. In thedrawings:

FIG. 1 is a diagram of an example approach for performing patientspecific implant matching.

FIGS. 2 and 50 are diagrams of example systems.

FIGS. 3, 4, 7, 16, 17, 29, 33, and 34 are flowcharts of exampleprocesses.

FIGS. 5, 6, 8-15, 18, 28, and 35-49 are diagrams of example interfaces.

FIG. 19 illustrates a knee box cut shape and size of the prior art.

FIGS. 20-27 illustrate an implant positioning template.

FIG. 30 illustrates an example three-dimensional outline representationof at least a portion of an outer surface of a periphery of athree-dimensional bone volume.

FIG. 31 illustrates an example two-dimensional outline representation ofa portion of an outer surface of a periphery of a three-dimensional bonevolume.

FIG. 32 illustrates an example of a segmented two-dimensional outlinerepresentation.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following description of the preferred embodiment(s) is merelyexemplary in nature and is in no way intended to limit the invention,its application, or uses.

Techniques are described for defining a set of implant sizes (e.g., kneeimplant sizes) that more accurately and completely fit bone resectionsmade during a surgical procedure (e.g., TKA). In defining the set ofimplant sizes, variability in bone resections (e.g., surgeon andinstrumentation variation) and manufacturing variation (e.g.,manufacturing tolerances) may be taken into account.

In some implementations, a broader range of implant sizes may begenerated by varying the perimeter of the implant to more closely matcha broader population of patients. In cases where the broader range ofsizes does not fit well enough, a “custom” implant may be made using thesame techniques used to make the discrete sizes in the broader sizeoffering. In addition, in some examples, instrument sizes may bedesigned to more accurately and completely fit bone resections madeduring a surgical procedure (e.g., TKA). In these examples, theinstrument sizes may be designed using techniques similar to thosediscussed throughout the application for implant sizes. The instrumentsizes may be designed in addition to implant sizes or as an alternativeto implant sizes.

In some examples, medical imaging (e.g., magnetic resonance imaging(MRI), computed tomography (CT), X-ray, Ultra-sound, etc.) is used tocreate a three-dimensional (3D) model of the patient's bone usingvarious Computer Aided Design (CAD) processes. In these examples, usinganalytical techniques (e.g. statistical shape analysis, 3D coordinateanalysis, matrix mathematical analysis, etc.) and summing process,anatomical, and surgical variations (e.g., tolerances or errors from avariety of sources), a 3D volume is modeled to intersect with thepatient bone model, and a solution volume is created that sums thesetolerances into a composite tolerance solution space. Further, in theseexamples, a bone surface ribbon is created from the solution volume anda BSpline is overlaid on the bone surface ribbon. The BSpline definesone new 3D solution curve that may be extruded to or from the instrumentmodel template (e.g., additive and/or subtractive processes) to create anew instrument perimeter size. To further refine the solution, similarlyshaped perimeters may be grouped together in subsets or clusters ofcases from which a final single solution size may be statisticallyderived.

FIG. 1 illustrates an example approach 100 for performing patientspecific implant matching. In the example approach 100, a systemmaintains a data repository 110 of sample three-dimensional bone imagedata. The data repository 110 may include many samples ofthree-dimensional bone image data taken from patients that haveundergone or considered an implant procedure and/or from cadavers aspart of a cadaver study. The three-dimensional bone image data mayinclude images of at least a portion of a bone that includethree-dimensional data or three-dimensional bone models generated basedon three-dimensional image data or other measurements of the portion ofthe bone. Each sample of three-dimensional bone image data included inthe data repository 110 corresponds to the same type of bone.

The system performs outline processing 120 on the samples ofthree-dimensional bone image data stored in the repository 110. Forexample, the system accesses a sample of three-dimensional bone imagedata and determines an outline representation of an outer surface of aperiphery of the bone represented in the sample. In this example, thesystem may use the techniques described below with respect to FIGS. 3-15to determine the outline representation.

After performing outline processing 120 on the samples ofthree-dimensional bone image data stored in the repository 110, thesystem stores outline representations of the samples in a database 130used for a library of implant designs. Once a significant number ofoutline representations have been stored in the database 130, the systemclusters the outline representations into groups having similarcharacteristics. Although three groups of outline representations areshown in FIG. 1 for brevity, many more groups of outline representationsmay result from clustering the outline representations stored in thedatabase 130. The system may use the techniques described below withrespect to FIG. 16 to cluster the outline representations.

After clustering the outline representations into multiple groups, thesystem defines an implant design for each group of outlinerepresentations and stores parameters that identify the implant designthat corresponds to the group and that enable the implant design to bematched against patient bone data. The parameters may define size andshape characteristics of a range of outline representations that match asize and shape of the implant design. The system may use the techniquesdescribed below with respect to FIG. 16 to define implant designs foreach group and store parameters associated with the defined implantdesigns.

In some examples, the database 130 defines a library of implant designsthat provides a match within a threshold degree for a relatively largepercentage of the population (e.g., seventy percent, eighty percent,ninety percent, etc.). In these examples, the high degree of coveragemay be obtained by considering a large number of samples in the datarepository 110 and clustering the outline representations into manydifferent groups within the database 130. In determining the degree ofcoverage, a patient may be deemed as covered by library of implantdesigns based on an implant design in the library being within athreshold match to the patient in terms of a type of fit, such asmillimeter gap from perimeter, percentage of surface area covered, ordiscrepancies at key landmarks. The system may be controlled to balancethe degree of coverage offered by the library of implant designs withthe cost of manufacturing standard implants for each of the groupswithin the database. For instance, the system may define an implantdesign for a particular group of outline representations only when thenumber of outline representations within the group reaches a thresholdnumber that justifies definition of a new implant design. Over time, thedegree of coverage offered by the library of implant designs maycontinue to expand as more and more bone data is collected and analyzed.As the library of implant designs expands, the library of implantdesigns may offer patient specific implant matching solutions to moreand more patients.

The system may use the library of implant designs stored in the database130 to select an implant design for a patient. For example, the systemaccesses three-dimensional bone data 140 for a patient, determines oneor more parameters 150 of the three-dimensional bone data 140, andmatches 160 the one or more parameters against the database 130. In thisexample, the system may determine an outline representation of thethree-dimensional bone data 140 and use the outline representation ofthe three-dimensional bone data 140 to match against the database 130.The system may use the techniques described below with respect to FIG.17 to determine 150 one or more parameters of the three-dimensional bonedata 140 and match 160 the one or more parameters against the database130.

The one or more parameters of the three-dimensional bone data 140 mayinclude any aspect of the three-dimensional bone data 140 that relatesto fit of an implant to the bone. For example, the one or moreparameters may include sensitivity to cut location, slope, andlikeliness for overhang. In this example, the system matches thesensitivity to cut location, slope, and/or likeliness for overhangagainst the database 130.

When the system determines that the one or more parameters of thethree-dimensional bone data 140 matches an implant design stored in thelibrary, the system outputs a message 170 indicating that a match hasbeen found. In the example shown in FIG. 1, the message 170 indicatesthat the second implant design has been selected as matching the patientbone data. In this regard, because the system selects an implant designthat matches the patient bone data within a threshold degree, the systemprovides a patient specific implant (or near patient specific implant)using a standard implant design without having to generate a customimplant. Because the system does not have to generate a custom implant,the cost and time related to obtaining a patient specific implant (ornear patient specific implant) may be reduced.

In some implementations, the system defines custom implants using thesame techniques described above. In these implementations, the systemmay pull modeling features to create the custom implant solution.

In addition to selecting an implant design for the patient, the systemalso adds 180 the three-dimensional bone data 140 to the data repository110. Accordingly, the system is able to continue to collect additionalsample data, which the system may use to redefine the implant designsincluded in the library stored in the database 130. As additional datais collected (e.g., when a threshold number of new samples has beencollected), the system repeats the clustering and implant designdefinition operations discussed above. In this regard, the system isable to routinely update the library of implant designs to add newimplant designs to cover new groups of patients and/or modify existingdesigns to better cover a group of patients or cover a larger group ofpatients. With these updates, the library of implant designs may expandand provide better coverage of the general population.

FIG. 2 illustrates an example implant analysis system 200, which may beused as the system referenced above with respect to FIG. 1. The system200 includes an input module 210, a data store 220, one or moreprocessors 230, one or more I/O (Input/Output) devices 240, and memory250. The input module 220 may be used to input any type of informationused in implant matching and processing. For example, the input module210 may be used to receive bone data and parameters related to implantmatching. In some implementations, data from the input module 210 isstored in the data store 220. The data included in the data store 220may include, for example, any type of implant related data (e.g., boneimages, three-dimensional models of bones, parameters related to implantdesigns, outline representations of a bone volume, etc.).

In some examples, the data store 220 may be a relational database thatlogically organizes data into a series of database tables. Each databasetable in the data store 220 may arrange data in a series of columns(where each column represents an attribute of the data stored in thedatabase) and rows (where each row represents attribute values). In someimplementations, the data store 220 may be an object-oriented databasethat logically or physically organizes data into a series of objects.Each object may be associated with a series of attribute values. In someexamples, the data store 220 may be a type of database management systemthat is not necessarily a relational or object-oriented database. Forexample, a series of XML (Extensible Mark-up Language) files ordocuments may be used, where each XML file or document includesattributes and attribute values. Data included in the data store 220 maybe identified by a unique identifier such that data related to aparticular process may be retrieved from the data store 220.

The processor 230 may be a processor suitable for the execution of acomputer program such as a general or special purpose microprocessor,and any one or more processors of any kind of digital computer. In someimplementations, the system 200 includes more than one processor 230.The processor 230 may receive instructions and data from the memory 250.The memory 250 may store instructions and data corresponding to any orall of the components of the system 200. The memory 250 may includeread-only memory, random-access memory, or both.

The I/O devices 240 are configured to provide input to and output fromthe system 200. For example, the I/O devices 240 may include a mouse, akeyboard, a stylus, or any other device that allows the input of data.The I/O devices 240 may also include a display, a printer, a 3D Printer,such as an SLS 3D printing machine that prints metal parts from a CADfile, or any other device that outputs data.

FIG. 3 illustrates a process 300 used in implant matching. Theoperations of the process 300 are described generally as being performedby the system 200. In some implementations, operations of the process300 may be performed by one or more processors included in one or moreelectronic devices.

The system 200 accesses a three-dimensional model of at least a portionof a bone (310). For example, the system 200 may access athree-dimensional model of an entire bone or a portion of a bone thatwas generated based on medical measuring of a bone of a patient. In thisexample, the system 200 may receive the three-dimensional model fromanother system that generates the three-dimensional model by processingmedical measurements taken of the bone or the portion of the bone. Themedical measurements may be determined based on medical imaging of thebone or other physical measuring of the bone using medicalinstrumentation.

In some examples, the system 200 generates the three-dimensional modelof an entire bone or a portion of a bone based on medical measuring ofthe bone of the patient. In these examples, the system 200 may accessone or more images of the portion of the bone and generate thethree-dimensional model of the portion of the bone based on the one ormore images of the portion of the bone. The one or more images of theportion of the bone may be captured using MRI, CT, X-ray, Ultra-sound,or other medical imaging technology. The system 200 may access the oneor more images of the portion of the bone from another system or maycapture the one or more images of the portion of the bone throughcontrol of an imaging device.

In some implementations, the system 200 may access MRI images thatdepict multiple slices of the portion of the bone. In theseimplementations, the system 200 may digitally create a mask of the MRIslices and stitch the MRI slices together to create a solid model.Further, in these implementations, the system 200 may remove errors andsmooth the data representing the solid model of the portion of the bone.In smoothing the data, the system 200 may select a minimum tool radiusto eliminate all smaller internal radii along the surface, includingdivots and wrinkles. The system 200 may use the smoothed version of thesolid model of the portion of the bone as the three-dimensional model ofthe portion of the bone. The application of a minimum tool radius to theshape of a three-dimensional model, curve, other spline forms, orinflexion points at intersections of these geometric forms may beapplied to the bone model or later to the implant model.

In implementations in which the techniques described throughout thisdisclosure are used in knee implants (e.g., TKA), the system 200accesses a three-dimensional model of at least a portion of a femurand/or a tibia. For instance, the system 200 may access athree-dimensional model of an entire femur or tibia, or may access athree-dimensional model of a portion of the femur or tibia located atthe knee joint (e.g., the portion of the femur or tibia that receives animplant during TKA). In addition, the techniques described throughoutthis disclosure may be applied to other types of implant procedures(e.g., hip replacement, shoulder replacement, etc.). For other types ofimplant procedures, the system 200 may access a three-dimensional modelof a portion of the bone that receives the implant, such as a portion ofthe bone located at a joint associated with the implant procedure. Insome implementations, a more comprehensive anatomical system also may beused that includes, for example, the entire leg, pelvis, and spine. Inthese implementations, by analyzing the entire system, the alignment offemur and tibia bone resections simulated by the system 200 may bealtered to account for motion of the knee joint taking into accountinput(s) from the entire anatomical system.

The system 200 defines a three-dimensional solution volume based onresection cuts used in fitting an implant on the portion of the bone(320). For example, the system 200 identifies a location of a plane ofeach resection cut needed to place an implant on the portion of the boneand defines a model that represents the locations of the resection cutsrelative to one another. In this example, the model that represents thelocations of the resection cuts relative to one another may define eachplane representing a resection cut as having a width component and aheight component.

In some implementations, to identify the location of the plane of eachresection cut needed to place the implant on the portion of the bone anddefine the model that represents the locations of the resection cutsrelative to one another, the system 200 determines one or more sizemeasurements of the portion of the bone and selects, from a library ofstandard implants, a standard implant appropriate for the one or moresize measurements of the portion of the bone. In these implementations,the system 200 accesses size and shape measurements for the standardimplant selected and uses the accessed size and shape measurements toidentify the location of the plane of each resection cut needed to placethe implant on the portion of the bone and define the model thatrepresents the locations of the resection cuts relative to one another.For instance, the system 200 defines the model to correspond to surfacesof the standard implant that contact the portion of the bone after theimplant has been placed on the portion of the bone.

To create the three-dimensional solution volume, the system 200 may adda thickness around each of the resection cuts to define athree-dimensional model in which each plane representing a resection cuthas a width component, a height component, and a thickness component.The shape of the volume represents at least a portion of the set of allpossible bone resections. In this regard, the volume may be oblong ortrapezoidal. The volume also may be tube-shaped, spherical, orbone-shaped or relatively prismoidal, as in a traditional saw bladeresection. The three-dimensional model may define a three-dimensionalgeometric shape that encompasses an area where resection cuts are madeto fit the implant on the portion of the bone. In adding the thicknessaround each of the resection cuts, the system 200 may add the thicknessuniformly on each side of the resection cut or may add the thicknessdisproportionately on sides of the resection cuts. The system 200 mayconsider the curvature of the bone and implant restrictions to set thethickness added to each resection cut and a distribution of the selectedthickness on sides of each resection cut. In considering the curvatureof the bone, the system 200 may use the curvature of the bone as part ofthe clustering and/or to partly drive the slope of the final implantdesign.

In some implementations, the system 200 may apply draft angle around theperimeter of the implant to match or more closely match adjacent boneslope. In these implementations, the system 200 attempts to match thedraft angle of an implant perimeter trim sheet in a 3D CAD model toadjacent bone/cartilage slope. For instance, the system 200 stores dataindicating draft angle for particular clusters of bones and then usesthe stored draft angle data to match draft angle for the particularclusters of bones. Draft angle matching may be applicable to a varietyof applications including knee femoral, tibial, and possibly patellarimplants, other joints (e.g., hip, ankle, shoulder, elbow, wrist, etc.),spine, plates (e.g., trauma, cranial, etc.), and prosthetic implantdevices for the purpose of skeletal reconstruction (e.g., cosmeticfacial reconstruction following an injury). A draft angle may be used insuch a way to avoid overhanging sharp edge features that could adverselyaffect adjacent soft tissues. Applying the composite tolerance volumeapproach described throughout this disclosure may ensure the sharp edgeoverhang risk is mitigated. Benefits of using a draft angle in this waymay include reducing unintended ligament strain by more closely matchingthe geometry of native bone in the joint or in other areas of thepatient's anatomy as in a cranial plate or a cosmetic facialreconstruction implant. In areas where soft tissues wrap around the edgeof an implant, more closely matching the native shape of the bone, andminimizing raised implant perimeter height and corner radii (CAD model“blends”), may further reduce risk of irritation, abrasion, or strain inadjacent soft tissue structures.

In some implementations, the system 200 may use patient specific draftangles, or draft angles determined from analysis, e.g. clusteringanalysis, of previous knee cases in the database. The system 200 may usea “standard library of implants” with many more sizes than previous kneeimplant systems with improved draft angles around the perimeter of theresection cuts. In these implementations, the system 200 may fit futurepatients with implants that more closely match resected bone volumes toimplant volumes. This may benefit patients by more closely matching softtissue (ligament) balance in the knee joint and preserving or improvingRange Of Motion (ROM) in the knee joint. In addition to adding draftangles to the perimeter, the system 200 also may increase the blendradii between the implant articular surfaces and the draft angleperimeter surfaces. Increasing the blend radii also may aid in moreclosely matching bone resection volume to implant volume.

In some examples, the system 200 may apply thickness (e.g., twomillimeters) along an entire portion of each resection cut. In theseexamples, the system 200 may define each resection cut as a rectangularbox and arrange the rectangular boxes at appropriate positions adjacentone another to define a three-dimensional box cut as thethree-dimensional solution volume.

For example, FIG. 5 illustrates an example interface 500 that shows athree-dimensional solution volume 520 that has a thickness of twomillimeters. As shown, the three-dimensional solution volume 520represents a three-dimensional box cut, which includes a rectangular boxdefined at each resection cut made to a distal end of a femur in TKA.For instance, the three-dimensional solution volume 520 has a firstrectangular box defined at an anterior cut, a second rectangular boxdefined at a distal chamfer cut, a third rectangular box defined at adistal cut, a fourth rectangular box defined at a posterior chamfer cut,and a fifth rectangular box defined at a posterior cut. The first,second, third, fourth, and fifth rectangular boxes are arranged atappropriate positions adjacent one another to define a three-dimensionalbox cut as the three-dimensional solution volume 520. Thethree-dimensional solution volume 520 may be one component of acomposite solution volume, which includes a bone model volume, a contactarea volume (e.g., from implant system designs), a manufacturingtolerance volume, an inspection tolerance volume, a surgeon variationvolume, and other volumes that represent other variability factors.

Each of the rectangular boxes that define the three-dimensional solutionvolume 520 has a width component, a height component, and a thicknesscomponent. For instance, as shown in FIG. 5, the first rectangular boxdefined at the anterior cut has a width component 530, a heightcomponent 540, and a thickness component 550. The width component 530and the height component 540 are defined based on a plane of theanterior cut and the thickness component 550 is defined by addingthickness around the plane of the anterior cut.

In addition, the system 200 may apply different thicknesses to differentresection cuts such that the system 200 defines the three-dimensionalbox cut with rectangular boxes having different thickness components.Further, the system 200 may apply different thicknesses along aparticular resection cut. In this regard, the particular resection cutis represented by a three-dimensional shape other than a rectangularbox. The system 200 may determine the thickness to apply along eachportion of each resection cut based on the curvature of the bone andimplant restrictions. The system 200 also may, additionally oralternatively, determine the thickness to apply along each portion ofeach resection cut based on tolerances related to a procedure forfitting the implant on the portion of the bone, as discussed in moredetail below.

In implementations in which the techniques described throughout thisdisclosure are used in knee implants (e.g., TKA), the system 200 maydefine a model that includes a plane for each of an anterior cut, adistal chamfer cut, a distal cut, a posterior chamfer cut, and aposterior cut needed to fit an implant on a distal end of a femur. Foreach of the anterior cut, the distal chamfer cut, the distal cut, theposterior chamfer cut, and the posterior cut, the system 200 may add athickness component proportionately on each side to define a rectangularbox cut that includes a rectangular box for each of the anterior cut,the distal chamfer cut, the distal cut, the posterior chamfer cut, andthe posterior cut.

In some implementations, the system 200 may use additional cuts as theimplant system requires. For instance, another knee system may requireseveral anterior chamfer planes. The system 200 also may consideradditional patient specific matching in the cruciate gap of the femur,and the anatomical features on the tibia and patella for a TKA.

In addition, the system 200 may consider corresponding anatomicalfeatures in other joints, spine, or other skeletal structures. Thesystem 200 may apply the techniques described throughout this disclosureto other extremities and surgical systems, such as IM nails, traumaplates/screws, cranial plates, cosmetic surgical prostheses, etc. Thesystem 200 may apply the techniques described throughout this disclosureto any surgical procedure where the system 200 can identify the geometryof an anatomical structure and apply it to a medical product design togive a patient specific solution.

Further, the “cuts” referred to in this disclosure may actually beplanes defined by the implant. For example, a surgeon may cut the bonelarge (resulting in smaller bone cut shape) and then impact a nominallysized implant onto the bone—compacting the surface down. In thisexample, the implant periphery might be made to fit the press-fitresection. However, the implant interfaces with all of the crushed boneand might ideally be made to match the bone shape at its final impactedlocation. Thus, the “cuts” referred to in this disclosure represent theplanes of the implant, rather than the actual cuts made during thesurgical procedure.

In some examples, the system 200 defines a three-dimensional tolerancevolume based on one or more tolerances for one or more variationsrelated to an implant procedure for placing the implant on the portionof the bone. In these examples, the system 200 may select the thicknessto add to each resection cut based on the one or more tolerances for theone or more variations related to an implant procedure for placing theimplant on the portion of the bone. The system 200 may select thethickness to cover a range of variations that may occur during animplant procedure due to surgeon error, manufacturing tolerances inmanufacturing the implant, variations in medical instrumentation, andvariations in modeling the portion of the bone in determining aplacement of the implant.

In addition, bone curvature may represent bone variation and mayinfluence a particular tolerance. For example, tolerance on the side ofthe bone where it is relatively steep would be more sensitive than atolerance applied to a relatively flat bony feature.

FIG. 4 illustrates a process 400 for defining a three-dimensionaltolerance volume. The process 400 may be used in defining athree-dimensional solution volume based on resection cuts used infitting an implant on the portion of the bone referenced above withrespect to reference numeral 320. The operations of the process 400 aredescribed generally as being performed by the system 200. In someimplementations, operations of the process 400 may be performed by oneor more processors included in one or more electronic devices.

The system 200 identifies one or more tolerances for one or morevariations related to an implant procedure for placing the implant onthe portion of the bone (410). For example, the system 200 may identifytolerances for any combination of variations, such as surgicalvariations and manufacturing variations, which control how accurately animplant procedure can be performed. In this example, the system 200 maydetermine a first tolerance related to variations in surgical techniquein performing the implant procedure (e.g., tolerances in an ability of asurgeon to make perfect incisions and cuts), a second tolerance relatedto variations in medical instrumentation used in performing the implantprocedure (e.g., tolerances in instrument manufacturing and wear), athird tolerance related to variations in manufacturing the implant usedin the implant procedure (e.g., manufacturing tolerances in how well animplant is made), a fourth tolerance related to variations in anatomy ofsimilar bones across patients, a fifth tolerance related to variationsin medical imaging used in generating the three-dimensional model of theportion of the bone (e.g., variation due to limitations on resolution ofan imaging device), and a sixth tolerance related to variations in fileconversion used in generating the three-dimensional model of the portionof the bone (e.g., variations that may be introduced when an originalimage file is converted into another format). The system 200 may use anycombination of one or more of the first tolerance, the second tolerance,the third tolerance, the fourth tolerance, the fifth tolerance, and thesixth tolerance in defining the three-dimensional tolerance volume.Also, the fifth tolerance related to variations in medical imaging mayinclude two components of medical imaging variation: (1) database sourcedata (e.g., imaging used to design the implant) and (2) new patient data(e.g., imaging of the patient receiving the patient specific implant).

In some implementations, the system 200 may determine the tolerances ofvariations based on general historical data related to implantprocedures tracked over time. In these implementations, the system 200may generally account for manufacturing tolerances, surgeon error,imaging tolerances, and file conversion tolerances without analyzing thespecific implant device or instrument used in the implant procedure, thesurgeon performing the implant procedure, the imaging technology used toimage the bone, or the specific file conversions needed in modeling thebone. Accordingly, in these implementations, the system 200 may accountfor tolerances related to variations associated with an implantprocedure by applying the same adjustments to each patient beingevaluated. In addition, the system 200 may determine the selection ofhow these objectives or rules are implemented based on ethnicity andother demographic or lifestyle metrics.

In other implementations, the system 200 may account for tolerancesrelated to variations associated with an implant procedure by tailoringadjustments to a specific implant procedure being evaluated. In theseimplementations, the system 200 may consider a tolerance of a specificsurgeon performing the implant procedure, a tolerance that accounts formanufacturing variation and wear of the medical instruments to be usedin the implant procedure, and a tolerance that accounts for variation inthe medical imaging and image processing operations performed inplanning the implant procedure. By accounting for the tolerancesspecific to the implant procedure, the system 200 may provide a moreaccurate adjustment for the potential variations associated with theimplant procedure. The system 200 may determine the specific tolerancesby receiving user input describing the tolerances or by receiving userinput describing characteristics of the implant procedure (e.g., surgeonname, equipment being used, imaging device being used, file conversionbeing performed in planning, instrument and implant materials, materialwear rates, manufacturing processes, inspection processes, etc.) andusing the inputted characteristics of the implant procedure to determinethe tolerances specific to the implant procedure.

The system 200 determines one or more measurements that account for theone or more tolerances identified (420). The system 200 may take a viewof a total continuum of tolerances related to the implant procedure andaccount for all of them in determining one or more measurements to usein generating the three-dimensional tolerance volume. In doing so, thesystem 200 may weigh the different tolerance values based on a degree ofaccuracy known for each tolerance value and a degree of possiblevariation known for each tolerance value. In addition, the system 200may consider a single tolerance value (or a subset of tolerance values)in determining one or more measurements to use in generating thethree-dimensional tolerance volume. The single tolerance value (or thesubset of tolerance values) may be selected based on a degree ofvariation associated with the tolerance value. For instance, tolerancerelated to surgeon error may be selected because a relatively highdegree of variation may result from surgeon error, as compared to othertolerances related to the implant procedure.

The system 200 may determine one or more measurements that account forthe one or more tolerances identified by determining a thickness to addto each resection cut in defining the tolerance volume. In determining athickness to add to each resection cut in defining the tolerance volume,the system 200 may determine a thickness that accounts for the toleranceof each potential variation considered. For example, the system 200 maydetermine a thickness of 0.2 mm to account for medical imaging based onan MRI imaging device having a tolerance of one pixel with a pixel sizeof 0.2 mm. In another example, the system 200 may determine a thicknessof 1.0 mm (e.g., +/−1.0 mm) to account for surgeon error based on areview of post-surgical data and/or surgeon comments indicating thatsurgeons are, on average, accurate to within 1.0 mm for resection cuts.After determining a thickness that accounts for the tolerance of eachpotential variation considered, the system 200 may sum all of thethicknesses to account for the worst case scenario in defining thetolerance volume. Alternatively, the system 200 may combine thethicknesses in a manner that accounts for the probability of eachvariation occurring and to what degree. For instance, the system 200 maycalculate a root mean square of the thicknesses and use the result asthe thickness added to the resection cuts in the tolerance volume. Thesystem 200 also may consider a distribution of errors related to theimplant procedure and determine a measurement that accounts for aparticular variation based on Monte Carlo analysis of sample errors forthe particular variation collected over time. In addition, theprobability of each variation could relate to the likelihood of any ofthe inputs described, including clusters of bones. As the system 200makes compromises between the resulting ribbons, the system 200 choosesa compromise that is most likely to match known and unknown bone shapes.For example, the system 200 may overlap ribbons and probabilitydistributions assigned to those ribbons. In this example, the overlapbetween the ribbons would consequently be overlap between probabilitydistributions as well. The combined probabilities (e.g., summed) givesthe system 200 a target that is better for the group even if itsub-optimal for individual group members.

The system 200 determines locations of resection cuts used in fittingthe implant on the portion of the bone (430). For example, the system200 determines a location of a plane of each resection cut needed toplace the implant on the portion of the bone. In this example, thesystem 200 may determine the location of the resection cuts based on ashape of the portion of the bone and/or a shape of typical resectioncuts needed to fit an implant on the portion of the bone. The system 200may use size and shape measurements of a standard implant to determinelocations of resection cuts, as discussed above with respect toreference numeral 320.

The system 200 defines the three-dimensional tolerance volume based onthe locations of the resection cuts and the one or more measurementsthat account for the one or more tolerances identified (440). Forexample, the system 200 may define a model of the resection cuts basedon the locations of the resection cuts. In this example, the system 200then may use the one or more measurements to add a thickness around eachof the resection cuts in the model of the resection cuts to define athree-dimensional model of the resection cuts in which each resectioncut has a width component, a height component, and a thicknesscomponent. In this regard, the three-dimensional model may define athree-dimensional geometric shape that encompasses an area whereresection cuts may occur in consideration of the tolerances of thevariations related to the implant procedure. In adding the thicknessaround each of the resection cuts, the system 200 may add the thicknessuniformly on each side of the resection cut (e.g., assume a perfect cutand expand the three-dimensional tolerance volume equal distances oneach side of the perfect cut). In addition, the system 200 may add thethickness disproportionately on sides of the resection cuts. The system200 may consider the curvature of the bone and implant restrictions inaddition to the tolerances to set the thickness added to each resectioncut and a distribution of the selected thickness on sides of eachresection cut.

In some examples, in accounting for tolerances, the system 200 may applythe same thickness (e.g., two millimeters) along an entire portion ofeach resection cut. In these examples, the system 200 may define eachresection cut as a rectangular box and arrange the rectangular boxes atappropriate positions adjacent one another to define a three-dimensionalbox cut as the three-dimensional model of the resection cuts.

In addition, the system 200 may apply different thicknesses to differentresection cuts such that the system 200 defines the three-dimensionalbox cut with rectangular boxes having different thickness components.For example, the tolerance related to surgeon error may be lower for afirst of the resection cuts as compared to a second of the resectioncuts. In this example, the system 200 may use a first thickness for thefirst of the resection cuts that is smaller than a second thickness usedfor the second of the resection cuts.

Further, the system 200 may apply different thicknesses along aparticular resection cut. In this regard, the particular resection cutis represented by a three-dimensional shape other than a rectangularbox. The system 200 may use different thicknesses along a particularresection cut if the tolerance for variations differs along theresection cut. For instance, the tolerance for surgeon error maygradually increase from a start of the particular resection cut to anend of the particular resection cut. In this instance, the system 200may gradually increase a thickness used along the particular resectioncut in defining the three-dimensional tolerance volume such that theportion of the three-dimensional tolerance volume corresponding to theparticular resection cut has a cone shape.

The system 200 may determine the thickness to apply along each portionof each resection cut based on the curvature of the bone, implantrestrictions, and the one or more measurements that account for the oneor more tolerances identified. In this regard, the system 200 may adjustthe one or more measurements that account for the one or more tolerancesidentified because the one or more measurements would result in issueswith the curvature of the bone and/or violate restrictions on how theimplant needs to be fit to the bone.

Referring again to FIG. 3, the system 200 intersects thethree-dimensional model of the portion of the bone with thethree-dimensional solution volume to produce a resultant bone volumerepresented in three dimensions (330). For instance, the system 200 maycompare the three-dimensional solution volume to the three-dimensionalmodel of the portion of the bone and determine an appropriate placementof the three-dimensional solution volume that aligns with locationswhere resection cuts would be made in placing an implant on the portionof the bone.

In aligning the three-dimensional solution volume, the system 200 mayalign the three-dimensional solution volume on a portion of thethree-dimensional model of the portion of the bone using techniquesdesigned to optimize placement of an articular surface of the implantwhen placed on the portion of the bone. Any type of technique foraligning the three-dimensional solution volume in a manner thatoptimizes placement of an articular surface of the implant may be used.For example, the system 200 may consider six degrees of freedom (e.g.,three location distances and three rotations) in aligning thethree-dimensional solution volume and may consider various aspects ofthe anatomy of the patient in selecting the alignment. In this example,the system 200 may consider a size and shape of the portion of the bone,a biomechanical axis relevant to the implant procedure, and appropriatemotions (or ranges of motion) for a joint associated with the portion ofthe bone. In considering the size and shape of the portion of the bone,the system 200 may consider the size and shape of the piece of bonebeing analyzed within the solution volume and/or consider the size andshape categorically. For instance, the system 200 may consider theresultant shape of sub-sampling a bone and/or may consider pristine boneshapes or geometric primitive(s).

In implementations in which the techniques described throughout thisdisclosure are used in knee implants (e.g., TKA), the system 200 mayconsider the varus-valgus angles, the flexion-extension angles, therotation positions, and any other parameters relevant to placement of animplant on the portion of the bone that results in optimized use of theknee after the implant procedure. In implementations in which thetechniques described throughout this disclosure are used in other typesof implants (e.g., spherically shaped hip joint bones, flat shouldercomponents, or saddle-shaped ankle joints), the system 200 may considercharacteristics relevant to placing the other types of implants.

As shown in FIG. 5, the example interface 500 shows a three-dimensionalmodel of a portion of a bone 510 intersected with the three-dimensionalsolution volume 520. As shown, the three-dimensional solution volume 520intersects the three-dimensional model of a portion of a bone 510 atpositions where resection cuts would be made in fitting an implant onthe portion of the bone. In this example, the three-dimensional model ofthe portion of the bone 510 models a distal end of a femur and thethree-dimensional solution volume 520 corresponds to resection cutsneeded to place a femoral component of a knee implant on the distal endof the femur modeled by the three-dimensional model 510.

After aligning the three-dimensional solution volume on thethree-dimensional model of the portion of the bone, the system 200 mayextract the portion of the three-dimensional model of the portion of thebone that intersects with the three-dimensional solution volume. Forinstance, the system 200 may remove portions of the three-dimensionalmodel of the portion of the bone that are outside of thethree-dimensional solution volume, thereby leaving the portion of thethree-dimensional model of the portion of the bone that intersects withthe three-dimensional solution volume. The system 200 may use theportion of the three-dimensional model of the portion of the bone thatintersects with the three-dimensional solution volume as the resultantbone volume, which is represented in three dimensions.

FIG. 6 illustrates an example interface 600 that shows a resultant bonevolume represented in three dimensions. The resultant bone volume shownin the interface 600 is a result of intersecting the three-dimensionalsolution volume 520 with the three-dimensional model of the portion ofthe bone 510, as shown in FIG. 5. The resultant bone volume shown in theinterface 600 models a shape (e.g., an anterior flange profile, profilesof the chamfer cuts, a distal cut profile, and a posterior cut profile)of what an outer surface of the bone would like after resection cuts aremade to the bone due to the tolerances.

Referring again to FIG. 3, the system 200 evaluates the resultant bonevolume with respect to one or more rules related to placing the implanton the portion of the bone (340) and adjusts the resultant bone volumebased on the evaluation of the resultant bone volume with respect to oneor more rules related to placing the implant on the portion of the bone(350). For example, the system 200 may access rules that define how theimplant should be placed on the bone to conform to preferred medicalpractices, what the shape of the implant should be to conform topreferred medical practices, and restrictions placed on the implant sizedue to manufacturing constraints. In this example, the system 200evaluates the resultant bone volume against the accessed rules anddetermines whether an implant fitted to portions of the resultant bonevolume would violate one or more of the accessed rules. Based on adetermination that an implant fitted to portions of the resultant bonevolume complies with all of the accessed rules, the system 200 maintainsthe resultant bone volume without adjustment.

Based on a determination that an implant fitted to portions of theresultant bone volume would violate one or more of the accessed rules,the system 200 determines whether the portions of the resultant bonevolume can be adjusted in a manner that complies with the accessedrules. Based on a determination that the portions of the resultant bonevolume can be adjusted in a manner that complies with the accessedrules, the system 200 adjusts the resultant bone volume (e.g., reshapesor removes portions of the resultant bone volume) in a manner thatcomplies with the accessed rules. Based on a determination that theportions of the resultant bone volume cannot be adjusted in a mannerthat complies with the accessed rules, the system 200 provides an alertthat indicates that the resultant bone volume violates one or more ofthe accessed rules and cannot be adjusted to comply with the accessedrules.

In some implementations, the rules related to placing the implant on theportion of the bone define an amount of contact needed to secure theimplant to the bone in accordance with preferred medical practices. Inthese implementations, the system 200 may access a minimum contact rulethat specifies a minimum contact area needed to stably secure theimplant on the portion of the bone. The system 200 compares the minimumcontact area defined by the minimum contact rule with the resultant bonevolume and, based on the comparison, determines whether all portions ofthe resultant bone volume meet the minimum contact area. Based on adetermination that all portions of the resultant bone volume meet theminimum contact area, the system 200 maintains the resultant bone volumewithout adjustment. However, based on a determination that portions ofthe resultant bone volume do not meet the minimum contact area, thesystem 200 adjusts the resultant bone volume by removing or reshapingthe portions of the resultant bone volume that do not meet the minimumcontact area.

In addition, the rules related to placing the implant on the portion ofthe bone may define an acceptable position of an articular surface ofthe implant in accordance with preferred medical practices. For example,the system 200 may access a rule that specifies a position and/or shapeof an articular surface of the implant that is needed for an acceptablesurgical result. In this example, the system 200 compares the positionand/or shape of the articular surface of the implant defined by the rulewith the resultant bone volume and, based on the comparison, determineswhether all portions of the resultant bone volume allow the implant tomeet the position and/or shape of the articular surface of the implantdefined by the rule. Based on a determination that all portions of theresultant bone volume meet the position and/or shape of the articularsurface of the implant defined by the rule, the system 200 maintains theresultant bone volume without adjustment. However, based on adetermination that portions of the resultant bone volume do not meet theposition and/or shape of the articular surface of the implant defined bythe rule, the system 200 adjusts the resultant bone volume by removingor reshaping the portions of the resultant bone volume that do not meetthe position and/or shape of the articular surface of the implantdefined by the rule. Adjusting the resultant bone volume to achieve anacceptable position and/or shape of an articular surface of the implantmay be important because, although a better fit to the bone may beachieved, the bone may have problems that are being corrected throughthe implant procedure and the benefits of having an improved articularsurface may outweigh the benefits of having a better fit to the bone.

In implementations in which the techniques described throughout thisdisclosure are used in knee implants (e.g., TKA), the system 200 mayaccess a rule that specifies a position and/or shape of a cruciate gapof the implant that is needed for an acceptable surgical result. In thisexample, the system 200 compares the position and/or shape of thecruciate gap of the implant defined by the rule with the resultant bonevolume and, based on the comparison, determines whether all portions ofthe resultant bone volume allow the implant to meet the position and/orshape of the cruciate gap of the implant defined by the rule. Based on adetermination that all portions of the resultant bone volume meet theposition and/or shape of the cruciate gap of the implant defined by therule, the system 200 maintains the resultant bone volume withoutadjustment. However, based on a determination that portions of theresultant bone volume do not meet the position and/or shape of thecruciate gap of the implant defined by the rule, the system 200 adjuststhe resultant bone volume by removing or reshaping the portions of theresultant bone volume that do not meet the position and/or shape of thecruciate gap of the implant defined by the rule. Adjusting the resultantbone volume to preserve the condylar width of the implant may beimportant to maintain acceptable articulation with respect to thepatellar component and to allow for enhanced ease of the implantprocedure by the surgeon. Adjusting the resultant bone volume topreserve the cruciate gap of the implant also may be useful.

In some examples, the rules related to placing the implant on theportion of the bone may define limitations on a risk of overhang allowedfor the implant. For instance, the system 200 may access a rule thatspecifies how close the implant may be to an edge of the bone. The rulemay have varying distances for different portions of the bone based onthe probability and severity of a risk of overhang at the particularportion of the bone (e.g., the rule may define more conservativedistances in locations near tissue where the risk of overhang isgreater). The system 200 compares the distances defined by the rule withthe resultant bone volume and, based on the comparison, determineswhether all portions of the resultant bone volume allow the implant tomeet the distances defined by the rule. Based on a determination thatall portions of the resultant bone volume meet the distances defined bythe rule, the system 200 maintains the resultant bone volume withoutadjustment. However, based on a determination that portions of theresultant bone volume do not meet the distances defined by the rule, thesystem 200 adjusts the resultant bone volume by removing or reshapingthe portions of the resultant bone volume that do not meet the distancesdefined by the rule. Adjusting the resultant bone volume to limit therisk of overhang may be important because overhang may result in patientdiscomfort after the implant procedure and may outweigh the benefits ofhaving a better fit to the bone.

In some implementations, the rules related to placing the implant on theportion of the bone may define limitations on a thickness of theimplant. For example, the system 200 may access a rule that specifies aminimum thickness of the implant. In this example, the system 200compares the thicknesses of an implant matched to the resultant bonevolume to the minimum thickness and, based on the comparison, determineswhether all portions of the resultant bone volume allow the implant tomeet the minimum thickness defined by the rule. Based on a determinationthat all portions of the resultant bone volume meet the minimumthickness defined by the rule, the system 200 maintains the resultantbone volume without adjustment. However, based on a determination thatportions of the resultant bone volume do not meet the minimum thicknessdefined by the rule, the system 200 adjusts the resultant bone volume byremoving or reshaping the portions of the resultant bone volume that donot meet the minimum thickness defined by the rule. The system 200 alsomay change the position of the final implant on the bone so that adifferent portion of the bone is sampled (e.g., resampling). Adjustingthe resultant bone volume to meet the minimum thickness may be importantbecause the negatives of having a thin portion of the implant (e.g., apotentially sharp edge, decreased strength, etc.) may outweigh thebenefits of having a better fit to the bone. Also, if matching bonevolume affects articulation, e.g. kinematics of femur/tibia/patellamotion, the system 200 may preserve some areas as “safe zones” topreserve stability of the knee joint. For example, the system 200 maypreserve the trochlear groove on the femoral implant for patellatracking.

Further, the rules related to placing the implant on the portion of thebone may define limitations on a shape of an edge of the implant. Forexample, the system 200 may access a rule that specifies an acceptablecontour of the implant. In this example, the system 200 compares thecontour of an implant matched to the resultant bone volume to theacceptable contour and, based on the comparison, determines whether allportions of the resultant bone volume allow the implant to meet theacceptable contour defined by the rule. Based on a determination thatall portions of the resultant bone volume meet the acceptable contourdefined by the rule, the system 200 maintains the resultant bone volumewithout adjustment. However, based on a determination that portions ofthe resultant bone volume do not meet the acceptable contour defined bythe rule, the system 200 adjusts the resultant bone volume by removingor reshaping the portions of the resultant bone volume that do not meetthe acceptable contour defined by the rule. Adjusting the resultant bonevolume to meet the acceptable contour may be important because thenegatives of having a sharp part of the implant may outweigh thebenefits of having a better fit to the bone.

FIG. 7 illustrates a process 700 for generating an adjusted bone volume.The process 700 may be used in evaluating the resultant bone volume withrespect to one or more rules related to placing the implant on theportion of the bone and adjusting the resultant bone volume based on theevaluation referenced above with respect to reference numerals 340 and350. The operations of the process 700 are described generally as beingperformed by the system 200. In some implementations, operations of theprocess 700 may be performed by one or more processors included in oneor more electronic devices.

The system 200 defines an acceptable zone based on a periphery of theimplant (710). For instance, the system 200 uses the implant peripheryto define a minimum acceptable zone, which may be smaller or larger thanexisting implants. The minimum acceptable zone may define a contact areaof the implant needed to achieve an acceptable surgical result thatconforms with preferred medical practices. The contact area may refer tothe contact area between the femoral implant and the femur. The system200 may define the minimum acceptable zone as a contact area volume thatmay be matched to the resultant bone volume. The contact area volume maydefine an area that accommodates a minimum size of articular surfaces ofthe implant.

The system 200 intersects the resultant bone volume with the acceptablezone to produce an acceptable bone volume (720). For instance, thesystem 200 may compare the resultant bone volume to the acceptable zoneand, based on the comparison, align the acceptable zone on the resultantbone volume. The system 200 may align the acceptable zone on theresultant bone volume by matching one or more surfaces of the acceptablezone with one or more surfaces of the resultant bone volume.

FIG. 8 illustrates an example interface 800 that shows athree-dimensional resultant bone volume 810 and a three-dimensionalacceptable zone 820. As shown, the three-dimensional acceptable zone 820intersects the three-dimensional resultant bone volume 810 with surfacesof the acceptable zone 820 aligned with surfaces of the resultant bonevolume 810. The acceptable zone 820 corresponds to a minimum size toprovide the necessary articular surfaces on the implant. Accordingly,the periphery of the acceptable zone 820 is added to the resultant bonevolume 810 where the periphery of the acceptable zone 820 extends beyondthe resultant bone volume 810. In some examples, the three-dimensionalacceptable zone 820 may be a contact area safe zone. In these examples,the contact area is mapped to where the tibia and patella contact thefemoral implant. In this regard, the system 200 protects this safe zoneso the kinematics and durability of an implant system are not changed.

Referring again to FIG. 7, the system 200 defines an implant tolerancezone based on sizing of the implant and one or more tolerances for oneor more variations related to an implant procedure for placing theimplant on the portion of the bone (730). For example, the system 200accesses size and shape data for a standard implant and defines theimplant tolerance zone based on the size and shape data for the standardimplant. In this example, the system 200 may extend the implanttolerance zone out from surfaces of the implant that contact the bone.The system 200 may define the implant tolerance zone using techniquessimilar to those described above for defining the three-dimensionaltolerance volume (see, e.g., FIG. 4 and the corresponding description).The system 200 may define the implant tolerance zone to have the samevolume as the three-dimensional tolerance volume described above.

FIG. 9 illustrates an example interface 900 that shows athree-dimensional representation of an implant 910, which may correspondto the largest limits placed on the implant size due to manufacturingconstraints, and a three-dimensional implant tolerance zone 920. Asshown, the three-dimensional implant tolerance zone 920 extends out fromsurfaces of the implant 910 that contact the bone and represents atolerance defined with respect to a size of the three-dimensionalrepresentation of the implant 910. The system 200 may define thethree-dimensional implant tolerance zone 920 using the same or similartechniques to those described above with respect to defining thethree-dimensional tolerance zone in FIG. 4.

Referring again to FIG. 7, the system 200 intersects the resultant bonevolume with the implant tolerance zone to produce an overlap bone volume(740). For instance, the system 200 may compare the resultant bonevolume to the implant tolerance zone and, based on the comparison, alignthe implant tolerance zone on the resultant bone volume. The system 200may align the implant tolerance zone on the resultant bone volume bymatching one or more surfaces of the implant tolerance zone with one ormore surfaces of the resultant bone volume.

FIG. 10 illustrates an example interface 1000 that shows athree-dimensional resultant bone volume 1010 and a three-dimensionalimplant tolerance zone 1020. As shown, the three-dimensional implanttolerance zone 1020 intersects the three-dimensional resultant bonevolume 1010 with surfaces of the implant tolerance zone 1020 alignedwith surfaces of the resultant bone volume 1010. The implant tolerancezone 1020 defines limits on the three-dimensional resultant bone volume1010. The system 200 may limit the resultant bone volume 1010 to a sizethat is within the implant tolerance zone 1020 to define athree-dimensional representation of an overlap bone volume. In theexample shown in FIG. 10, the three-dimensional overlap bone volumerepresents an intersection of the resultant bone volume described abovewith respect to FIG. 6 with the implant tolerance zone 920 describedabove with respect to FIG. 9.

Referring again to FIG. 7, the system 200 combines the acceptable bonevolume of FIG. 8 with the overlap bone volume of FIG. 10 to produce acomposite bone volume (750). For instance, the system 200 may comparethe acceptable bone volume to the overlap bone volume and, based on thecomparison, align the acceptable bone volume on the overlap bone volumeto produce the composite bone volume. The system 200 may align theacceptable bone volume on the overlap bone volume by matching one ormore surfaces of the acceptable bone volume with one or more surfaces ofthe overlap bone volume.

FIG. 11 illustrates an example interface 1100 that shows athree-dimensional representation of a composite bone volume in which anacceptable bone volume has been aligned on an overlap bone volume. Inthe example shown in FIG. 11, the composite bone volume has been definedbased on a combination of the three-dimensional acceptable bone volumedescribed above with respect to FIG. 8 with the overlap bone volumedescribed above with respect to FIG. 10.

Referring again to FIG. 7, the system 200 uses the composite bone volumeto generate an adjusted bone volume that defines inner and outertolerance in three dimensions (760). For instance, the system 200removes and/or reshapes portions of the composite bone volume that donot meet the acceptable zone and the implant tolerance zone. The system200 may use the composite bone volume to define inner and outeracceptable three-dimensional tolerance for a particular region (e.g.,the anterior flange of a distal end of a femur) or to define inner andouter acceptable three-dimensional tolerance for the entire implant andall associated faces/edges. Where needed, the system 200 may create aninterpolation of the tolerance zone, which adds to the bone volume. Thesystem 200 may produce an adjusted bone volume that results fromremoving and/or reshaping portions of the composite bone volume that donot meet the acceptable zone and the implant tolerance zone.

FIG. 12 illustrates an example interface 1200 that shows athree-dimensional representation of an adjusted bone volume. In theexample shown in FIG. 12, the three-dimensional adjusted bone volumeshows a bone volume adjusted in accordance with the composite bonevolume described above with respect to FIG. 11. In this example, thesystem 200 removed portions of the composite bone volume that did notmeet the implant tolerance zone and added portions to the composite bonevolume where the composite bone volume did not meet the acceptable zone.

Referring again to FIG. 3, the system 200 determines an outlinerepresentation of at least a portion of an outer surface of a peripheryof the resultant bone volume (360). For example, the system 200 mayanalyze the resultant bone volume (e.g., the adjusted bone volumedescribed above) and identify an outer surface of a periphery of theresultant bone volume. In this example, the system 200 may extract, fromthe resultant bone volume, the outer surface of the periphery of theresultant bone volume to create a bone surface ribbon that models theouter surface of the periphery of the resultant bone volume. The bonesurface ribbon may be represented in three dimensions and may representan outer surface of an implant that best matches the portion of the bonebeing evaluated while accounting for the tolerances and rules describedthroughout this disclosure. The bone surface ribbon may be used as theoutline representation.

FIG. 13 illustrates an example interface 1300 that shows a bone surfaceribbon. In the example shown in FIG. 13, the bone surface ribbon is athree-dimensional representation of an outer surface of a periphery ofthe adjusted bone volume shown in FIG. 12. In this example, the system200 has extracted the bone surface ribbon from the adjusted bone volumeshown in FIG. 12 to model a perimeter of an implant that best matchesthe adjusted bone volume shown in FIG. 12 while accounting for thetolerances and rules described throughout this disclosure.

In some implementations, the system 200 fits a curve to the bone surfaceribbon to define the outline representation. In these implementations,the system 200 may use statistics or other appropriate techniques toselect a shape for an implant to fit the bone surface ribbon and may fita curve to the selected shape. For instance, the system 200 may create acurve that follows a sheet or tolerance volume represented by the bonesurface ribbon. The system 200 may define the curve in three dimensions.

In some examples, the system 200 may fit a curve to the bone surfaceribbon without limiting the curve to the surface of the ribbon. In theseexamples, the system 200 may allow the curve to extend inside and/oroutside the bone surface ribbon within a tolerance value (e.g., twomillimeters) and derive a curve that best matches the bone surfaceribbon within the tolerance value. The system 200 may define thetolerance to a side of the bone surface ribbon that limits a potentialfor overhang of an implant created using the derived curve. Forinstance, to avoid overhang, the system 200 may only place the curveinside the bone surface ribbon, rather than outside the bone ribbon.

To fit a curve to the bone surface ribbon, the system 200 may overlay aBSpline (or other type of spline) on the bone surface ribbon. Forinstance, the system 200 may analyze the bone surface ribbon and, basedon the analysis, identify locations on the bone surface ribbonappropriate for nodes of a spline. The system 200 then may create thespline by defining curves that model the bone surface ribbon between theidentified nodes.

FIG. 14 illustrates an example interface 1400 that shows a bone surfaceribbon 1410 with a curve 1420 overlaid on the bone surface ribbon 1410.The curve 1420 represents a three-dimensional fit to the bone surfaceribbon 1410 and includes portions that extend outside and inside of thebone surface ribbon 1410 within a tolerance zone. The curve 1420 is aBSpline overlaid on the bone surface ribbon 1410.

In some implementations, the system 200 determines the outlinerepresentation for only a portion of the outer surface of the peripheryof the resultant bone volume. In these implementations, the system 200may create a partial bone surface ribbon for the portion of the outersurface of the periphery of the resultant bone volume and may fit acurve to the partial bone surface ribbon. The system 200 also may createa complete bone surface ribbon for the entire outer surface of theperiphery of the resultant bone volume and fit a curve to only a portionof the complete bone surface ribbon. The system 200 further may create acomplete bone surface ribbon for the entire outer surface of theperiphery of the resultant bone volume, fit a curve to an entirety ofthe complete bone surface ribbon, and then select a portion of the curvethat corresponds to the portion of the outer surface of the periphery ofthe resultant bone volume.

The system 200 may select the portion of the outer surface of theperiphery of the resultant bone volume based on user input that definesa portion of the resultant bone volume of interest to a user. Forexample, the system 200 may receive user input that defines a part ofthe outer surface of the periphery of the resultant bone volume ofinterest. In this example, the part may correspond to a part of theouter surface of the periphery where variation occurs and the benefitsof fitting an implant at the part of the outer surface of the peripheryoutweigh the risks of doing so, such as risking overhang by attempting aclose fit or disrupting an articulating surface of the implant. In thisregard, the system 200 may select non-articulating surfaces or edges ofthe resultant bone volume and/or portions of the resultant bone volumewhere a risk of tissue damage due to overhang is lower.

In implementations in which the techniques described throughout thisdisclosure are used in knee implants (e.g., TKA), the system 200 mayselect a portion of the outer surface of the periphery of a femur thatcorresponds to the anterior flange. The portion of the outer surface ofthe periphery of the femur that corresponds to the anterior flange maybe of interest because significant variation of the anterior flangeexists among different patients and the downside of fitting an implantto the anterior flange is limited since the portion of the implantfitted to the anterior flange is not an articulating surface.

FIG. 15 illustrates an example interface 1500 that shows a portion of acurve 1510 created to model a portion of a bone surface ribbon. Thecurve 1510 represents a three-dimensional fit to a portion of a bonesurface ribbon located at an anterior flange of a femur bone. The curve1510 is a BSpline overlaid on a portion of a bone surface ribbon locatedat an anterior flange of a femur bone.

Referring again to FIG. 3, the system 200 uses the outlinerepresentation in one or more operations related to implant matching(370). For instance, the system 200 may design a custom implant based onthe outline representation, use the outline representation in generatinga library of implants, and/or use the outline representation to select,from a library of implants, an implant to use in an implant procedure.In designing a custom implant, the system 200 may input the outlinerepresentation to an implant manufacturing application and the implantmanufacturing application may generate a design of an implant thatcorresponds to the outline representation. In this regard, the system200 may input a spline that defines the outline representation and theimplant manufacturing application may generate additional splines usedto develop the custom implant.

In some examples, the outline representation may represent an entireouter surface of a periphery of a resultant bone volume. In theseexamples, the system 200 generates a design of a custom implant in whichan entire periphery of the custom implant corresponds to the outlinerepresentation. In other examples, the outline representation mayrepresent a portion of an outer surface of a periphery of a resultantbone volume. In these examples, the system 200 generates a design of acustom implant in which a portion of the periphery of the custom implantcorresponds to the outline representation and the remaining portion ofthe periphery of the custom implant corresponds to a standard implantdesign.

In some implementations, the system 200 offsets the outlinerepresentation in designing an implant. In these implementations, thesystem 200 may slightly reduce how far the outer surface of the outlinerepresentation extends (e.g., slightly shrinks the outlinerepresentation) and may use the reduced version of the outlinerepresentation as a basis for designing the implant. The system 200 maydefine the amount of reduction in accordance with implant manufacturingtolerances to reduce the risk of manufacturing variations causing theimplant to overhang at one or more portions of the bone. For example,the system 200 may offset a bone surface ribbon (or a curve fitted to abone surface ribbon) by two millimeters prior to using the bone surfaceribbon (or the curve fitted to the bone surface ribbon) to generate animplant design. Offsetting the bone surface ribbon may be necessary toaccount for differences between the source data and the actual size ofpatient bones versus the CAD models. In offsetting the bone surfaceribbon, the system 200 may offset the implant model perimeterapproximately 3.5 mm inside the bone model perimeter.

FIG. 16 illustrates a process 1600 for generating a library of implantdesigns. The process 1600 may be used in using the outlinerepresentation in one or more operations related to implant matchingreferenced above with respect to reference numeral 370. The operationsof the process 1600 are described generally as being performed by thesystem 200. In some implementations, operations of the process 1600 maybe performed by one or more processors included in one or moreelectronic devices.

The system 200 stores the outline representation in a database withsample outline representations determined for other bone portions thatcorrespond to the portion of the bone (1610). For instance, the system200 maintains a database of sample outline representations for aparticular bone, or subgroup or cluster of bones (e.g., a femur or adistal end of a femur) and adds the determined outline representation tothe database. The sample outline representations may include outlinerepresentations determined for many different patients, includingoutline representations determined for bones of cadavers analyzed duringa cadaver study. The sample outline representations may be completeoutline representations for the particular bone or partial outlinerepresentations for the particular bone (e.g., an anterior flangeprofile of a distal end of femur). The system 200 also may store, in thedatabase, other patient information related to the patient (e.g., age,gender, ethnicity, weight, height, etc.) and/or information related tothe particular bone (e.g., size measurements of the particular bone).The system 200 may use the other patient information to assist ingrouping the sample outline representations and matching a new patientto a grouping of the sample outline representations.

The system 200 analyzes characteristics of the outline representationsstored in the database (1620). For example, the system 200 determinessize and/or shape characteristics of the sample outline representationsstored in the database and compares the determined size and/or shapecharacteristics of the sample outline representations to one another. Inthis example, the system 200 determines a level of similarity betweensample outline representations based on the comparison.

In some implementations, the system 200 uses size and/or shapecharacteristics of entire sample outline representations in performingthe analysis. In other implementations, the system 200 uses size and/orshape characteristics of portions of sample outline representations inperforming the analysis. For instance, the system 200 may select asubset of positions along the sample outline representations and usesize and/or shape characteristics of each of the subset of positions inthe analysis. In implementations in which the techniques describedthroughout this disclosure are used in knee implants (e.g., TKA), thesystem 200 may select several points along a representation of ananterior flange, determine location information of each of the severalpoints, and use the location information in the analysis.

Based on the analysis, the system 200 clusters the outlinerepresentations stored in the database into multiple groups that eachincludes outline representations having similar characteristics (1630).For instance, the system 200 uses a clustering process to group thesample outline representations into multiple, different groups of sampleoutline representations that have similar size and/or shapecharacteristics. The system 200 may perform the clustering based on thecomparison of size and/or shape characteristics of the sample outlinerepresentations. The system 200 may perform clustering by assigning aset of sample outline representations into groups (called clusters), sothat the sample outline representations in the same cluster are moresimilar (in some sense or another) to each other than to those in otherclusters.

Any type of one or more clustering processes may be used to arrange thesample outline representations into groups having similar size and/orshape characteristics. For instance, the system 200 may use a machinelearning process to group sample outline representations with similarcharacteristics together. Example clustering processes the system 200may use include one or more of connectivity-based clustering processes(e.g., hierarchical clustering processes), such as single-linkageclustering, complete linkage clustering, and average linkage clustering,centroid-based clustering processes, such as k-means clustering,k-medians clustering, and Fuzzy c-means clustering, distribution-basedclustering processes, such as expectation-maximization (EM) clusteringand mixture of Gaussians clustering, and density-based clusteringprocesses, such as density-based spatial clustering of applications withnoise (DBSCAN) and ordering points to identify the clustering structure(OPTICS).

The system 200 defines an implant design for each of the multiple groups(1640). For example, after the sample outline representations have beenclustered into multiple groups with similar characteristics, the system200 determines an implant design for a particular group using the sampleoutline representations included in the particular group. In thisexample, the system 200 may analyze characteristics of the sampleoutline representations included in the particular group and determine abest fit outline representation for the sample outline representationsincluded in the particular group. The system 200 then may use the bestfit outline representation to define an implant design for theparticular group using the techniques described above with respect todefining a custom implant using an outline representation. Afterdefining the implant design for the particular group, the system 200continues processing other groups of outline representations until animplant design has been defined for each of the groups.

In some implementations, to define an implant design for a group ofoutline representations, the system 200 may compute an average outlinerepresentation by averaging the outline representations included in thegroup. In these implementations, the system 200 may use the averageoutline representation to define an implant design for the particulargroup using the techniques described above with respect to defining acustom implant using an outline representation.

In addition, to define an implant design for a group of outlinerepresentations, the system 200 may use minimum and maximum criteria ofthe outline representations included in the group. For instance, thesystem 200 may define a combined outline representation based on minimumand maximum points of each of the outline representations included inthe group such that all of the outline representations included in thegroup fit within the combined outline representation.

In some examples, the rules applied to generate a particular implantdesign include user needs constraints specifying where around theimplant boundary or perimeter that implant overhang beyond bone cutperimeters and bone underhang beyond the implant boundary or perimeterby boundary zone are specified. These boundary constraints address risksincluding soft tissue risk, load transmission from implant to cortical(more dense outer bone), minimizing blood loss, and other known risks.Design team surgeons may evaluate and validate the designs and thesystem 200 may adapt the designs based on user input specifyingrecommendations of the design team surgeons.

After defining an implant design for each of the multiple groups, thesystem 200 may evaluate the defined implant designs for each group. Forexample, after the system 200 has defined an implant design for aparticular group, the system 200 may compare the implant design to eachof the outline representations included in the particular group and,based on the comparison, determine how closely the implant designmatches each of the outline representations included in the particulargroup. Based on the determinations of how closely the implant designmatches each of the outline representations included in the particulargroup, the system 200 may determine whether the implant design matcheseach of the outline representations included in the particular groupwithin a threshold degree. Based on a determination that the implantdesign matches each of the outline representations included in theparticular group within the threshold degree, the system 200 determinesthat the implant design is sufficient for the particular group andassigns the implant design to the particular group.

However, based on a determination that the implant design does not matchone or more of the outline representations included in the particulargroup within the threshold degree, the system 200 may reject the implantdesign and provide an alert indicating the implant design isinsufficient for the particular group. After rejecting the implantdesign, the system 200 may attempt to use another technique to generatea new implant design based on the outline representations included inthe particular group. The system 200 may evaluate the new implant designto determine whether the new design matches each of the outlinerepresentations included in the particular group within the thresholddegree. The system 200 may continue to attempt new implant designs forthe particular group until the system 200 determines that an implantdesign matches each of the outline representations included in theparticular group within the threshold degree or that all techniques forgenerating an implant design based on the outline representationsincluded in the particular group have been attempted without success.

In some examples, after rejecting the implant design or afterdetermining that all techniques for generating an implant design basedon the outline representations included in the particular group havebeen attempted without success, the system 200 determines to performadditional clustering on the outline representations included in theparticular group to divide the particular group into smaller groups ofoutline representations. In these examples, the system 200 repeats theclustering operations described above with parameters that result in acloser degree of similarity between the outline representations in thegroups. After reclustering, the system 200 repeats the operationsdescribed above with respect to generating an implant design for eachgroup and evaluating implant designs until an acceptable implant designhas been defined for each group.

In some implementations, after rejecting the implant design or afterdetermining that all techniques for generating an implant design basedon the outline representations included in the particular group havebeen attempted without success, the system 200 may remove problematicoutline representations from the particular group such that the implantdesign matches each of the remaining outline representations included inthe particular group within the threshold degree. In theseimplementations, the system 200 may attempt to cluster removed outlinerepresentations into other groups (e.g., new groups) or may determine toleave the removed outline representations without a correspondingimplant design in the library. For example, the system 200 may determineto stop clustering and defining new implant designs when the library ofavailable implant designs covers a threshold percentage (e.g., eightypercent) of sample outline representations within a threshold degree. Inthis example, the system 200 may determine that a custom implant isneeded for patients having similar outline representations to theremoved outline representations that do not have a corresponding implantdesign in the library.

In some examples, the system 200 may receive new sample outlinerepresentations from new patients and/or may receive feedback on fits ofimplants selected from the library of implants. In these examples, thesystem 200 may use the new sample outline representations from newpatients and/or the feedback on fits of implants selected from thelibrary of implants to update the clustering of sample outlinerepresentations in the database and define (or redefine) implant designsto expand the coverage of the library of implant designs.

The system 200, for each implant design, stores the implant design inassociation with one or more parameters that enable matching of theimplant design with patient bone data (1650). For instance, the system200 may store, in association with data identifying the implant design,a best fit outline representation or an average outline representationfor the outline representations included in the group corresponding tothe implant design. The system 200 also may store, in association withdata identifying the implant design, a range of outline representationdata that covers outline representations that fit within the groupcorresponding to the implant design. The system 200 further may store,in association with data identifying the implant design, bone sizemeasurements and other patient data (e.g., age, gender, ethnicity,weight, height, etc.) that may be useful in determining whether or not apatient matches the implant design. The system 200 may store any type ofdata that enables matching of patient bone data to an implant in thelibrary of implants.

Although the process 1600 described above with respect to FIG. 16addresses clustering using outline representations, similar techniquesmay be used with other types of data that is descriptive of bone shapeand size. For example, the system 200 may perform clustering usinglandmark sets. In this example, the system 200 uses landmarks in lieu ofoutline representations (e.g., BSplines) at the first stage wherecharacterizing the bone cut shapes before the system 200 cluster casesof similar size and shape. After clustering based on landmarks, thesystem 200 creates corresponding “High Resolution” outlinerepresentations (e.g., BSplines), making one “High Resolution” outlinerepresentation (e.g., BSpline) that fits each bone in a cluster ofcases. The system 200 then applies known tolerances (e.g., manufacturingtolerances, surgeon variability, inspection tolerances, imagingtolerances, etc.) to the “High Resolution” outline representation (e.g.,BSpline), and creates a corresponding “Low Resolution” outlinerepresentation (e.g., BSpline) that accounts for the tolerances.

From the “Low-Resolution” outline representation (e.g., BSpline), thesystem 200 creates an implant design. For instance, the system 200creates a new boundary or perimeter trim sheet that cuts away or adds tothe existing femoral implant model to make a new patient or clusterspecific femoral implant that satisfies the rules for the particularcluster. Each cluster then has: (1) a High Resolution outlinerepresentation (e.g., BSpline), (2) Low Resolution outlinerepresentation (e.g., BSpline), and (3) Femoral Implant Model. Theoutline representation (e.g., BSpline) may be defined using aUniGraphics (UG) Expression List that can be generated using programmingcode, such as a MatLab or Visual Basic program implemented on a computersystem. The UG Expression List generation may be done using an automatedprocess as described above.

In some examples of clustering the bones, the system 200 may cluster bybone (e.g., lining up similarly shaped bones) or the system 200 maycluster the features themselves relative to some global reference frame.For example, the system 200 may line up all of the bones according toexisting surgical protocols and extract the radius of the posteriorcondyles from a set of multiple clusters (e.g., fifty clusters). Thesystem 200 may use more resolution on the anterior flange since theanterior flange has a higher degree of variation in the population.Accordingly, the system 200 may use more clusters for the anteriorflange feature (e.g., four hundred clusters of that feature). Infeature-based clustering, the features used may correspond to a featurefound in the CAD model to model the implant (or instrument) or a featurein the manufacturing process (e.g., second operation grindingoperation).

Along those same lines, the system 200 may include a minimum includedtool radius to prevent the solution spline from having wrinkles ordivots that are not manufacturable. This may be one of the drivingfactors behind why the curve 1420 is depicted as not following the“ribbon” exactly.

FIG. 17 illustrates a process 1700 for matching patient data to animplant. The process 1700 may be used in using the outlinerepresentation in one or more operations related to implant matchingreferenced above with respect to reference numeral 370. The operationsof the process 1700 are described generally as being performed by thesystem 200. In some implementations, operations of the process 1700 maybe performed by one or more processors included in one or moreelectronic devices.

The system 200 determines one or more parameters of the outlinerepresentation (1710). For instance, the system 200 may determine sizeand/or shape characteristics of the outline representation. The system200 also may determine position data for portions of the outlinerepresentation that enables matching to implants in the library. Thesystem 200 may determine any type of parameters that enable matching ofthe outline representation to an implant in the library of implants,including the parameters stored in association with implant designs inthe process 1600. The system 200 may use the outline representationitself as the one or more parameters of the outline representation.

The system 200 compares the one or more parameters of the outlinerepresentation to parameters associated with available implant designs(1720) and, based on comparison results, determines whether the one ormore parameters of the outline representation match an available implantdesign within a threshold degree (1730). For instance, the system 200may access parameters stored in association with implant designs in thelibrary of implant designs and compare the one or more parameters of theoutline representation to the accessed parameters. Based on thecomparison of the one or more parameters of the outline representationto the accessed parameters, the system 200 determines whether the one ormore parameters of the outline representation match the accessedparameters within a threshold degree.

In some examples, the system 200 may compare a shape of the outlinerepresentation to shapes of outer perimeters of implant designs storedin the library of implant designs. In these examples, based on thecomparison of the shape of the outline representation to shapes of outerperimeters of implant designs stored in the library of implant designs,the system 200 determines whether the shape of the outlinerepresentation exactly matches a shape of an outer perimeter of animplant design stored in the library or matches a shape of an outerperimeter of an implant design stored in the library within a thresholdtolerance zone (e.g., matches the outer perimeter within two millimetersat all locations).

In some implementations, the system 200 may determine size measurementsof the portion of the bone and first compare the determined sizemeasurements to sizes of implant designs stored in the library. In theseimplementations, the system 200 may, based on the comparison, select asubset of implant designs within the library that are acceptable for thedetermined size measurements. Although each of the subset of implantdesigns is acceptable for the size of the portion of the bone, each ofthe subset of implant designs has a different shape for an outerperimeter of the implant design. Accordingly, after selecting thesubset, the system 200 performs a second comparison to select theimplant design that best matches a shape of the portion of the bone. Inthis regard, the system 200 compares the one or more parameters of theoutline representation to parameters associated with each of the subsetof implant designs to assess whether a shape of the outlinerepresentation matches a shape of any of the subset of implant designs.

Based on a determination that the one or more parameters of the outlinerepresentation match the available implant design within the thresholddegree, the system 200 outputs the available implant design as matchingthe outline representation (1740). For instance, the system 200 maydisplay the matching implant design to a surgeon (or other medical careprovider) for use in an implant procedure. If the system 200 determinesthat multiple implant designs match the outline representation withinthe threshold degree, the system 200 may display each of the multipleimplant designs to enable a surgeon to select the preferred implantdesign for the implant procedure.

Based on a determination that the one or more parameters of the outlinerepresentation do not match an available implant design within thethreshold degree, the system 200 determines that a custom implant isneeded and outputs a message that indicates a custom implant is needed(1750). For instance, the system 200 may display a message indicatingthat no match was found in the library of implants. The system 200 alsomay initiate a process to define a custom implant for the portion of thebone based on the determination that the one or more parameters of theoutline representation do not match an available implant design withinthe threshold degree.

FIG. 18 illustrates an example interface 1800 that shows athree-dimensional implant design 1810, a plane 1820 that corresponds toa face of the implant design 1810, and a curve 1830 that has beenprojected onto the face of the implant design 1810. The curve 1830 is athree-dimensional outline representation of an anterior flange of adistal end of a femur. As shown, the curve 1830 does not match the outerperiphery of the implant design 1810 at the plane 1820 that correspondsto the face of the implant design 1810. Accordingly, the system 200updates the implant design 1810 to have a shape that matches the curve1830. The system 200 may use the updated implant design to define acustom implant that has an outer periphery that matches the curve 1830.

FIG. 19 illustrates a medial-lateral (ML) positioning template 2200. TheML positioning template 2200 is also known as an ML positioner. The MLpositioning template 2200 is used to locate the custom implant or animplant design from a library of many discrete sizes on the distal endof a femur in a medial-lateral position. The perimeter shape of the MLpositioner 2200 is determined using the same methodology as describedabove for the implant. The shape of the ML positioner perimeter can bedefined using a BSpline or some other 3-dimensional curve definitionconvention. In one example, a BSpline defines one new 3D solution curvethat can be extracted from the implant model template to create a newimplant perimeter size and a new ML positioner. Both the implant and theML positioner can be designed in a single CAD model or in separate CADmodels with perimeter shape(s) defined by the same BSpline. In thepreferred embodiment, the ML positioner perimeter shape matches that ofthe implant, but in some embodiments, the ML positioner could have anoffset inward or outward relative to the implant perimeter. As examples,the offset may be 1-4 mm, more narrowly 1-2 mm, or about 2 mm. In someembodiments, the ML Positioner includes articular surfaces, thuscombining the ML centering function and the ligament balancing into oneinstrument. In some embodiments, only a portion of the ML positionermatches the shape of the implant. For example, only the medial andlateral perimeter match in shape and as such each of the medial andlateral perimeters have a patient specific shape.

The bone facing side of the ML positioner has a standard box cut shapeand size. A typical box cut shape and size is shown in FIG. 23. Thetypical box cut shape includes an anterior-posterior distal cut surfaceAPDC, a posterior chamfer surface PC, an anterior chamfer surface AC,posterior condyle surfaces PCON, and an anterior flange surface AF. AFextends anteriorly relative to the coronal plane at an angle α. Theproximal P and distal D directions are also illustrated. The dimensionsof the box cut shape and size for the ML Positioner depends upon theparticular knee system selected.

Referring once again to FIG. 19 and also to FIGS. 20-22, the MLpositioner 2200 has locating openings 2210. The locating openings 2210are used to create holes in the distal end of the femur such that thepatient specific knee implant is centered on the distal femur. Thelocating openings 2210 may take the form of holes, slots, overlappingholes, or combination slots that allow for variance in themedial-lateral and anterior-posterior directions. In the depictedembodiment, the locating openings 2210 are shown as holes. In someembodiments, the ML positioner has pin holes 2220. Although pin holes2220 are depicted as circular holes, they may have some other shape,such as a slot. In some embodiments, the ML positioner includes a ribstiffener 2230. The ML positioner includes at least one paddle 2250,posterior chamfer portion 2240, distal cut surface portion 2260,anterior chamfer portion 2270, and anterior flange portion 2280. In someembodiments, stiffeners 2290 extend around lug openings 2210 and extendacross the anterior chamfer portion 2270, the distal cut surface portion2260, the posterior chamfer portion 2240, and the at least one paddle2250. In some embodiments, the ML positioner includes notch 2245, and insuch embodiments, the posterior chamfer portion includes a posteriorlateral chamfer and a posterior medial chamfer, and the at least onepaddle includes a posterior medial condyle and a posterior lateralcondyle

Referring to FIGS. 24-27, the ML positioner is placed on the prepareddistal femur, and the locating holes 2210 are used to create lug holesin the distal femur. In some embodiments, the ML positioner is placedsuch that the perimeter of the ML positioner matches the perimeter ofthe distal femur. In some embodiments, the ML positioner perimeter isoffset inwardly relative to the perimeter of the distal femur. In otherembodiments, only portions of the ML positioner perimeter match portionsof the distal femur perimeter. In yet other embodiments, the distal cutportion of the ML positioner is centered relative to the overall widthof the distal portion of the femur. A distal tip 2310 of a punch 2300 isinserted into the locating holes 2210 of the ML positioner 2200 tocreate holes in the distal femur that receive the implant.Alternatively, the holes in the distal femur may be drilled or reamed.In some embodiments, the ML positioner may be pinned in place usingholes 2220 and pins 2400 (as best seen in FIGS. 26 and 27). As best seenin FIG. 27, the ML positioner also can serve as a first check of box cutshape and size for verifying the AP dimension and oblique length ofchamfer cuts. By using the ML Positioner to locate the femoral implantlug holes, a centered fit of the implant is achieved.

Once the femoral implant lug holes are drilled, reamed, and/or punchedthrough the use of the ML Positioner and into the distal face of theresected femur, the ML positioner is removed and the femoral articulartrial is placed on the femur to evaluate ligament balance and range ofmotion. Following ligament balancing, the patient specific femoralimplant is secured in placed on the distal femur using bone cement or analternative fixation method.

FIG. 28 illustrates an example interface 1900 that shows three views1900A, 1900B, 1900C, 1900D, 1900E, 1900F and 1900G of a patient specificimplant placed on a distal end of a femur. The patient specific implantmay be a custom implant designed using the techniques describedthroughout this disclosure or an implant matched from a library ofimplants using the techniques described above with respect to FIG. 17.The patient specific implant is a femoral component placed on the distalend of a femur in TKA. As shown, the patient specific implant closelymatches the bone resection around the perimeter of the implant/boneinterface.

Although the examples described throughout this disclosure largely applyto knee implants and TKA, the techniques described throughout thisdisclosure may be applied to other implant procedures and joints, suchas hips, ankles, shoulders, and spine. Although the example cuts havebeen portrayed as sawblade cuts, the cuts may be accomplished by ashaver, reamer, or burr and similar techniques may be used. The solutionzone also may be flat as depicted in the examples or some other shape.For example, the zone might be in the shape of a hollow sphere for thehead of the hip joint.

Further, in some implementations, a technique is described for creatingpatient specific implant shapes that closely match the boundaries ofbone resections. The technique creates the boundaries by assemblingdiscrete curves, splines, or segments of the bone resection boundariesinto a complete bone resection boundary corresponding to the patientspecific implant perimeter shape and size. Assembling the discretecurves, splines, or segments of the bone resection boundaries into thecomplete bone resection boundary may reduce or eliminate implantoverhang beyond the bone resection boundaries and/or underhang of bonebeyond the boundaries of the patient specific implant shape and sizewith a specified minimum underhang to allow for bone cut variations.

In some examples, the modular approach of assembling discrete segmentsof the bone resection boundaries into a complete implant perimeter shapeand size allows for a broader set of discrete implant sizes that willfit a broader population of patients. By reducing the individualboundary segments into localized groupings of spline segments, thequantity of computer numerical control (CNC) programs required tomanufacture implants also may be reduced, making the storage of splinesegment libraries more manageable while offering more discrete sizes tothe surgeon and patient.

In addition, the modular patient specific implant sizing methodology andtechnique may include clustering of data and assembling selected clustermodules or “buckets” into a complete implant boundary curve orExpression List. Any clustering or assembling technology may be used.And, the technique may be a structured technique for organization ofbone cut data and the structured output of 3D CAD model Expression Liststhat define the implant perimeter/boundary shapes and sizes specific topatient specific implant designs.

FIG. 29 illustrates a process 2900 used in implant matching. Theoperations of the process 2900 are described generally as beingperformed by the system 200. In some implementations, operations of theprocess 2900 may be performed by one or more processors included in oneor more electronic devices.

The system 200 accesses a three-dimensional model of at least a portionof a bone (2910). For example, the system 200 may access athree-dimensional model of an entire bone or a portion of a bone thatwas generated based on medical measuring of a bone of a patient. In thisexample, the system 200 may receive the three-dimensional model fromanother system that generates the three-dimensional model by processingmedical measurements taken of the bone or the portion of the bone. Themedical measurements may be determined based on medical imaging of thebone or other physical measuring of the bone using medicalinstrumentation.

In some examples, the system 200 generates the three-dimensional modelof an entire bone or a portion of a bone based on medical measuring ofthe bone of the patient. In these examples, the system 200 may accessone or more images of the portion of the bone and generate thethree-dimensional model of the portion of the bone based on the one ormore images of the portion of the bone. The one or more images of theportion of the bone may be captured using MRI, CT, X-ray, Ultra-sound,or other medical imaging technology. The system 200 may access the oneor more images of the portion of the bone from another system or maycapture the one or more images of the portion of the bone throughcontrol of an imaging device.

In some implementations, the system 200 may access MRI images thatdepict multiple slices of the portion of the bone. In theseimplementations, the system 200 may digitally create a mask of the MRIslices and stitch the MRI slices together to create a solid model.Further, in these implementations, the system 200 may remove errors andsmooth the data representing the solid model of the portion of the bone.In smoothing the data, the system 200 may select a minimum tool radiusto eliminate all smaller internal radii along the surface, includingdivots and wrinkles. The system 200 may use the smoothed version of thesolid model of the portion of the bone as the three-dimensional model ofthe portion of the bone.

In implementations in which the techniques described throughout thisdisclosure are used in knee implants (e.g., TKA), the system 200accesses a three-dimensional model of at least a portion of a femurand/or a tibia. For instance, the system 200 may access athree-dimensional model of an entire femur or tibia, or may access athree-dimensional model of a portion of the femur or tibia located atthe knee joint (e.g., the portion of the femur or tibia that receives animplant during TKA). In addition, the techniques described throughoutthis disclosure may be applied to other types of implant procedures(e.g., hip replacement, shoulder replacement, etc.). For other types ofimplant procedures, the system 200 may access a three-dimensional modelof a portion of the bone that receives the implant, such as a portion ofthe bone located at a joint associated with the implant procedure.

The system 200 determines a three-dimensional bone volume based on thethree-dimensional model of the portion of the bone and resection cutsused in fitting an implant on the portion of the bone (2920). Forexample, the system 200 analyzes the three-dimensional model of theportion of the bone and identifies locations on the three-dimensionalmodel where resection cuts would be made in fitting an implant on theportion of the bone. In this example, the system 200 determines thethree-dimensional bone volume as the portion of the three-dimensionalmodel that corresponds to the locations of the resection cuts. Thesystem 200 may account for tolerances and variations involved in fittingan implant on the portion of the bone in determining thethree-dimensional bone volume. For instance, the system 200 may accountfor the tolerances and variations by defining a range of locations forthe resection cuts that fit within the tolerances and variations. Then,the system 200 may determine the three-dimensional bone volume as theportion of the three-dimensional model that corresponds to the ranges oflocations for the resection cuts. In some implementations, techniquessimilar to those described above with respect to reference numerals 320to 350 in FIG. 3 and FIGS. 4-12 may be used in determining thethree-dimensional bone volume based on the three-dimensional model ofthe portion of the bone and resection cuts used in fitting an implant onthe portion of the bone.

The system 200 determines a three-dimensional outline representation ofat least a portion of an outer surface of a periphery of thethree-dimensional bone volume (2930). For example, the system 200 mayanalyze the three-dimensional bone volume and identify an outer surfaceof a periphery of the three-dimensional bone volume. In this example,the system 200 may extract, from the three-dimensional bone volume, theouter surface of the periphery of the three-dimensional bone volume tocreate a bone surface ribbon that models the outer surface of theperiphery of the three-dimensional bone volume. The bone surface ribbonmay be represented in three dimensions and may represent an outersurface of an implant that best matches the portion of the bone beingevaluated while accounting for the tolerances and rules describedthroughout this disclosure. The bone surface ribbon may be used as theoutline representation. In some implementations, techniques similar tothose described above with respect to reference numeral 360 in FIG. 3and FIGS. 13-15 may be used in determining the three-dimensional outlinerepresentation of the portion of the outer surface of the periphery ofthe three-dimensional bone volume.

FIG. 30 illustrates an example three-dimensional outline representation3000 of at least a portion of an outer surface of a periphery of athree-dimensional bone volume. In this example, the portion of the bonecorresponds to a distal end of a femur. As shown, FIG. 30 provides anisometric view of a three-dimensional box cut on a distal end of afemur. The three-dimensional box cut has been labelled in five segmentsthat correspond to the resection cuts used in determining thethree-dimensional box cut. For instance, a first segment, “I,”corresponds to an anterior flange cut segment, a second segment, “II,”corresponds to an anterior chamfer cut segment, a third segment, “III,”corresponds to a distal cut segment, a fourth segment, “IV,” correspondsto a posterior chamfer cut segment, and a fifth segment, “V,”corresponds to a posterior condyles cut segment. In this example, toassemble the complete bone cut boundary shape for a femoral implant, amodular approach is taken to characterize bone resection boundary shapeand size.

Referring again to FIG. 29, the system 200 converts thethree-dimensional outline representation into a two-dimensional outlinerepresentation of the portion of the outer surface of the periphery ofthe three-dimensional bone volume (2940). For instance, the system 200processes the three-dimensional outline representation to flatten orproject the three-dimensional outline representation onto atwo-dimensional plane. In flattening or projecting the three-dimensionaloutline representation onto a two-dimensional plane, the system 200orients each segment of the three-dimensional outline representation tobe parallel to one another with edges of adjacent segments aligned.

In some examples, the system 200 converts the three-dimensional outlinerepresentation into a two-dimensional outline representation that has athickness to account for one or more tolerances for one or morevariations related to an implant procedure for placing the implant onthe portion of the bone. In these examples, the system 200 determines athickness needed to account for the one or more tolerances for the oneor more variations and defines the two-dimensional outlinerepresentation to have the determined thickness. The thickness may varyacross the two-dimensional outline representation as the tolerances forvariations may be different at different portions of the two-dimensionaloutline representation.

In some implementations, the system 200 offsets the two-dimensionaloutline representation to reduce the likelihood of overhang of theimplant on the portion of the bone. In these implementations, the system200 offsets the two-dimensional outline representation away from edgesof the bone to reduce the likelihood of overhang. The system 200 may usean offset of two millimeters to reduce the likelihood of overhang whileproviding a suitable fit.

FIG. 31 illustrates an example two-dimensional outline representation3100 of a portion of an outer surface of a periphery of athree-dimensional bone volume. In this example, the portion of the bonecorresponds to a distal end of a femur. As shown, FIG. 31 shows thethree-dimensional box cut from FIG. 30 converted to two dimensions on asingle plane. The plane may have a thickness making it athree-dimensional composite volume to account for variation in boneresections. The two-dimensional box cut (with potential thickness) hasbeen labelled in five segments that correspond to the resection cutsused in determining the two-dimensional box cut. For instance, a firstsegment, “I,” corresponds to an anterior flange cut segment, a secondsegment, “II,” corresponds to an anterior chamfer cut segment, a thirdsegment, “III,” corresponds to a distal cut segment, a fourth segment,“IV,” corresponds to a posterior chamfer cut segment, and a fifthsegment, “V,” corresponds to a posterior condyles cut segment. Inaddition, a location of the cruciate gap center on the two-dimensionalbox cut has been illustrated.

Referring again to FIG. 29, the system 200 segments the two-dimensionaloutline representation into segments that correspond to the resectioncuts used in fitting the implant on the portion of the bone (2950). Forexample, the system 200 identifies locations of edges of adjacentresections cuts on the two-dimensional outline and separates thetwo-dimensional outline at the located edges. In this example, eachsegment corresponds to a particular resection cut and includes datarepresenting an outline of the bone at the particular resection cut. Theoutline data for a resection cut may be a continuous line or may bebroken up into multiple different lines. For instance, for eachresection cut, the outline data may represent a first outline of thebone at a lateral side and a second outline of the bone at a medialside. Data representing the resection cut boundaries may or may not bestored as part of the segments of the two-dimensional outlinerepresentation.

In implementations in which the portion of the bone is a distal end of afemur, the system 200 segments the two-dimensional outlinerepresentation into five different segments. In this regard, the system200 segments the two-dimensional outline representation into a firstsegment that corresponds to a distal face of the distal end of thefemur, a second segment that corresponds to an anterior chamfer of thedistal end of the femur, a third segment that corresponds to a posteriorchamfer of the distal end of the femur, a fourth segment thatcorresponds to an anterior flange of the distal end of the femur, and afifth segment that corresponds to posterior condyles of the distal endof the femur.

FIG. 32 illustrates an example of a segmented two-dimensional outlinerepresentation 3200. In this example, the portion of the bonecorresponds to a distal end of a femur. As shown, FIG. 32 shows thetwo-dimensional box cut from FIG. 31 separated into five “buckets” ofspline segments; namely, one group for each face of the box cut. Thesegmented two-dimensional box cut (with potential thickness) has beenlabelled in five segments that have been separated. For instance, afirst segment, “I,” corresponds to an anterior flange cut segment, asecond segment, “II,” corresponds to an anterior chamfer cut segment, athird segment, “III,” corresponds to a distal cut segment, a fourthsegment, “IV,” corresponds to a posterior chamfer cut segment, and afifth segment, “V,” corresponds to a posterior condyles cut segment. Inaddition, a location of the cruciate gap center on the segmentedtwo-dimensional box cut has been illustrated.

Referring again to FIG. 29, the system 200 performs one or moreoperations related to implant matching based on the segments thatcorrespond to the resection cuts used in fitting the implant on theportion of the bone (2960). For instance, the system 200 may design acustom implant based on the segments, use the segments in generating alibrary of implants, and/or use the segments to select, from a libraryof implants, an implant to use in an implant procedure. In designing acustom implant, the system 200 may input outline data for each of thesegments to an implant manufacturing application and the implantmanufacturing application may generate a design of an implant thatcorresponds to the outline data. In this regard, the system 200 mayinput multiple spline segments that define the outline data and theimplant manufacturing application may generate additional splines usedto develop the custom implant. The implant manufacturing application maystart with the segment that requires the best fit to obtain an implantwith the best fit on that segment and then work outward to segments thatdo not require as good a fit or whose fit is dependent on the segmentthat requires the best fit. For instance, in designing a custom femoralcomponent of a knee implant, the system 200 may start within the segmentcorresponding to the distal face, define the portion of the implant forthe distal face, then define the portion of the implant for the anteriorand posterior chamfers, and finally define the portion of the implantfor the anterior flange and posterior condyles.

In some implementations, the system 200 offsets the segments indesigning an implant. In these implementations, the system 200 mayslightly reduce how far the outer surface of outline data for thesegments extends (e.g., slightly shrinks the outline data) and may usethe reduced version of the outline data as a basis for designing theimplant. The system 200 may define the amount of reduction in accordancewith implant manufacturing tolerances to reduce the risk ofmanufacturing variations causing the implant to overhang at one or moreportions of the bone. For example, the system 200 may offset outlinedata by two millimeters prior to using the outline data to generate animplant design. Offsetting the outline data may be necessary to accountfor differences between the source data and the actual size of patientbones versus the CAD models. In offsetting the outline data, the system200 may offset the implant model perimeter approximately 3.5 mm insidethe bone model perimeter.

In implementations in which the portion of the bone is a distal end of afemur, each of the five buckets or segments is clustered into groups ofsimilar shape and size or shape independent of size. To fit a newpatient, the complete implant bone cut boundary is then reassembledstarting with the best matching distal face (bucket III), and thenadding the best matching anterior chamfer and posterior chamfer to thedistal face, and finally adding the anterior flange and posteriorcondyles. To achieve a best possible fit all around the bone cutboundary, the medial-lateral width, “x”, for each bucket, e.g. x1 forbucket “I”, x2 for bucket “II”, x3 for bucket “III”, x4 for bucket “IV”,x5 for bucket “V”, can be changed to best match the patient's distalfemur medial-lateral size. To align the cruciate gap of the implant withthe cruciate gap of the femur, a “cruciate gap center” (C.G. Ctr) islandmarked. After the complete bone cut boundary is assembled, it isanalytically verified to meet underhang and overhang constraintsspecified for the patient specific knee implant system. Once verified,the CNC code for the total bone cut boundary is compiled with a standardlibrary of CNC code for articular surfaces, box cut features, lugs, andother geometric features, and the implant is machined using CNC machinetools, much the same as a standard Legion® femoral implant would bemachined. Medial-Lateral positioning instruments, e.g. a ML Positioner,can be made using the same bone cut boundary shapes and sizes as thefemoral implant.

In some examples, by reducing the total number of “pre-programmed” CNCfiles to a smaller set, e.g., ten to twenty programs per bucket per boxcut size, management of programs may be more efficient, and the totalnumber of possible discrete implant sizes is significantly larger,improving the fit for a larger population of patients, e.g. twentyspline pairs per bucket*five buckets*five box cut sizes*two hands (leftand right)*two implant families (CR & PS)=total two thousand sizes, andfive hundred CNC programs. This example assumes programs can include a“mirror” feature for doing left and right hand sizes from the same baseprogram.

FIG. 33 illustrates a process 3300 for generating a library of implantdesigns. The process 3300 may be used in performing one or moreoperations related to implant matching based on the segments thatcorrespond to the resection cuts used in fitting the implant on theportion of the bone referenced above with respect to reference numeral2960. The operations of the process 3300 are described generally asbeing performed by the system 200. In some implementations, operationsof the process 3300 may be performed by one or more processors includedin one or more electronic devices.

The system 200 stores each segment in a database with sample segmentsdetermined for the particular resection cut on other bone portions thatcorrespond to the portion of the bone associated with the segment(3310). For instance, the system 200 maintains a database of sampleoutline data for segments corresponding to a particular resection cutfor a particular bone (e.g., a first bucket of segments for an anteriorflange of a distal end of a femur, a second bucket of segments for ananterior chamfer of a distal end of a femur, a third bucket of segmentsfor a distal face of a distal end of a femur, a fourth bucket ofsegments for a posterior chamfer of a distal end of a femur, and a fifthbucket of segments for posterior condyles of a distal end of a femur)and adds each segment to the appropriate portion of the database (e.g.,the appropriate bucket). The sample outline data may include outlinedata determined for many different patients, including outline datadetermined for bones of cadavers analyzed during a cadaver study. Thesample outline data may correspond to segments of the particular bone(e.g., an anterior flange profile of a distal end of femur). The system200 also may store, in the database, other patient information relatedto the patient (e.g., age, gender, ethnicity, weight, height, etc.)and/or information related to the particular bone (e.g., sizemeasurements of the particular bone). The system 200 may use the otherpatient information to assist in grouping the sample outline data foreach resection cut and matching a new patient to a grouping of thesample segments.

The system 200, for each resection cut, analyzes characteristics of thesegments stored in the database for the resection cut (3320). Forexample, the system 200 determines size and/or shape characteristics ofthe sample segments stored in the database and compares the determinedsize and/or shape characteristics of the sample segments to one another.In this example, the system 200 determines a level of similarity betweensample segments based on the comparison.

In some implementations, the system 200 uses size and/or shapecharacteristics of entire sample segments in performing the analysis. Inother implementations, the system 200 uses size and/or shapecharacteristics of portions of sample segments in performing theanalysis. For instance, the system 200 may select a subset of positionsalong the sample segments and use size and/or shape characteristics ofeach of the subset of positions in the analysis. In implementations inwhich the techniques described throughout this disclosure are used inknee implants (e.g., TKA), the system 200 may select several pointsalong a representation of an anterior flange, determine locationinformation of each of the several points, and use the locationinformation in the analysis.

The system 200, based on the analysis, clusters the segments stored inthe database for the resection cut into multiple groups that eachincludes segments having similar characteristics (3330). For instance,the system 200 uses a clustering process to group the sample segmentsinto multiple, different groups of sample segments that have similarsize and/or shape characteristics. The system 200 may perform theclustering based on the comparison of size and/or shape characteristicsof the sample segments. The system 200 may perform clustering byassigning a set of sample segments into groups (called clusters), sothat the sample segments in the same cluster are more similar (in somesense or another) to each other than to those in other clusters.

Any type of one or more clustering processes may be used to arrange thesample segments into groups having similar size and/or shapecharacteristics. For instance, the system 200 may use a machine learningprocess to group sample segments with similar characteristics together.Example clustering processes the system 200 may use include one or moreof connectivity-based clustering processes (e.g., hierarchicalclustering processes), such as single-linkage clustering, completelinkage clustering, and average linkage clustering, centroid-basedclustering processes, such as k-means clustering, k-medians clustering,and Fuzzy c-means clustering, distribution-based clustering processes,such as expectation-maximization (EM) clustering and mixture ofGaussians clustering, and density-based clustering processes, such asdensity-based spatial clustering of applications with noise (DBSCAN) andordering points to identify the clustering structure (OPTICS).

After clustering, each bucket of segments for each resection cut hasmultiple groups of segments arranged in the bucket. For instance, inimplementations in which the portion of the bone is a distal end of afemur, the segments in a first bucket corresponding to the anteriorflange are clustered into multiple groups, the segments in a secondbucket corresponding to the anterior chamfer are clustered into multiplegroups, the segments in a third bucket corresponding to the distal faceare clustered into multiple groups, the segments in a fourth bucketcorresponding to the posterior chamfer are clustered into multiplegroups, and the segments in a fifth bucket corresponding to theposterior condyles are clustered into multiple groups.

The system 200 defines, for each resection cut, a representation ofclustered segments for each of the multiple groups (3340). For example,after the sample segments have been clustered into multiple groups withsimilar characteristics, the system 200 determines a representation ofclustered segments for each group. In this example, the system 200 mayanalyze characteristics of each group and determine a best fitrepresentation for the sample segments included in the particular group.After defining the representation for the particular group, the system200 continues processing other groups of segments until a representationhas been defined for each of the groups for each of the resection cuts.

In some implementations, to define a representation for a group ofsegments, the system 200 may compute an average representation byaveraging data descriptive of the segments included in the group. Inaddition, to define a representation for a group of segments, the system200 may use minimum and maximum criteria of the segments included in thegroup. For instance, the system 200 may define a combined representationbased on minimum and maximum points of each of the segments included inthe group such that all of the segments included in the group fit withinthe combined representation.

After defining a representation for each of the multiple groups, thesystem 200 may evaluate the defined representation for each group. Forexample, after the system 200 has defined a representation for aparticular group, the system 200 may compare the implant design to eachof the segments included in the particular group and, based on thecomparison, determine how closely the representation matches each of thesegments included in the particular group. Based on the determinationsof how closely the representation matches each of the segments includedin the particular group, the system 200 may determine whether therepresentation matches each of the segments included in the particulargroup within a threshold degree. Based on a determination that therepresentation matches each of the segments included in the particulargroup within the threshold degree, the system 200 determines that therepresentation is sufficient for the particular group and assigns therepresentation to the particular group.

However, based on a determination that the representation does not matchone or more of the segments included in the particular group within thethreshold degree, the system 200 may reject the representation andprovide an alert indicating the representation is insufficient for theparticular group. After rejecting the representation, the system 200 mayattempt to use another technique to generate a new representation basedon the segments included in the particular group. The system 200 mayevaluate the new representation to determine whether the newrepresentation matches each of the segments included in the particulargroup within the threshold degree. The system 200 may continue toattempt new representations for the particular group until the system200 determines that a representation matches each of the segmentsincluded in the particular group within the threshold degree or that alltechniques for generating a representation based on the segmentsincluded in the particular group have been attempted without success.

In some examples, after rejecting the representation or afterdetermining that all techniques for generating a representation based onthe segments included in the particular group have been attemptedwithout success, the system 200 determines to perform additionalclustering on the segments included in the particular group to dividethe particular group into smaller groups of segments. In these examples,the system 200 repeats the clustering operations described above withparameters that result in a closer degree of similarity between thesegments in the groups. After reclustering, the system 200 repeats theoperations described above with respect to generating a representationfor each group and evaluating representations until an acceptablerepresentation has been defined for each group.

In some implementations, after rejecting the representation or afterdetermining that all techniques for generating a representation based onthe segments included in the particular group have been attemptedwithout success, the system 200 may remove problematic segments from theparticular group such that the implant design matches each of theremaining segments included in the particular group within the thresholddegree. In these implementations, the system 200 may attempt to clusterremoved segments into other groups (e.g., new groups) or may determineto leave the removed segments without a corresponding representation inthe library. For example, the system 200 may determine to stopclustering and defining new representations when the library covers athreshold percentage (e.g., eighty percent) of sample segments within athreshold degree.

In some examples, the system 200 may receive new sample segments fromnew patients. In these examples, the system 200 may use the new samplesegments from new patients to update the clustering of sample segmentsin the database and define (or redefine) representations to expand thecoverage of the library.

The system 200 accesses representations of clustered segments thatinclude a representation of clustered segments for a single groupdefined for each of the resection cuts (3350). For example, the system200 accesses one representation for each resection cut such that thesystem 200 accesses a set of representations that corresponds to allsegments needed for an implant. The system 200 may access everycombination of the groups of clustered segments in designing implantdesigns or may access a subset of the potential combinations. Inaccessing a subset of the potential combinations, the system 200 mayconsider characteristics of the representations of the clusteredsegments and only uses representations that are similar enough togenerate a reasonably useful implant design. For instance, the system200 may consider the medial-lateral width of the representations and usecombination in which all representations have a medial-lateral widththat is within a threshold degree.

The system 200 reassembles the accessed representations into atwo-dimensional outline representation of the portion of the bone(3360). For instance, the system 200 reverses the process used tosegment the two-dimensional outline representation of the portion of thebone and regenerates a two-dimensional outline representation based onthe accessed representations. In some examples, the system 200identifies locations of edges of segments corresponding to adjacentresections cuts and joins the segments at the located edges. In theseexamples, the system 200 may align the widths of the adjacent segment asbest as possible and may smooth the resulting two-dimensional outlinerepresentation at points of discontinuity caused by slight differencesin widths of the segments. The system 200 may determine a reassembledtwo-dimensional outline representation that represents a best fit of theaccessed representations.

In some implementations, the two-dimensional outline representationreferenced in the present application may refer to discrete landmarkpoints, rather than a complete outline. In these implementations,three-dimensional bone surface ribbons and discrete landmark points maybe reduced to a two-dimensional dataset by, for example, ignoring theZ-coordinate. The reduced two-dimensional (x,y) data from thethree-dimensional bone surface ribbons may be applied to the approachesto modular clustering and implant matching described throughout thisdisclosure.

The system 200 generates an implant design based on the reassembledtwo-dimensional outline representation of the portion of the bone(3370). For example, after the sample segments have been clustered intomultiple groups with similar characteristics for each resection cut, thesystem 200 determines an implant design for a particular set of groupsusing the reassembled two-dimensional outline representation for theparticular set of groups. The system 200 then may use the reassembledtwo-dimensional outline representation to define an implant design forthe particular set of groups using the techniques described above withrespect to defining a custom implant using an outline representation.After defining the implant design for the particular set of groups, thesystem 200 continues processing other sets of groups of segments untilan implant design has been defined for each potential combination ofgroups or for each potential combination of groups that are similarenough to generate a reasonably useful implant design.

In some examples, the rules applied to generate a particular implantdesign include user needs constraints specifying where around theimplant boundary or perimeter that implant overhang beyond bone cutperimeters and bone underhang beyond the implant boundary or perimeterby boundary zone are specified. These boundary constraints address risksincluding soft tissue risk, load transmission from implant to cortical(more dense outer bone), minimizing blood loss, and other known risks.Design team surgeons may evaluate and validate the designs and thesystem 200 may adapt the designs based on user input specifyingrecommendations of the design team surgeons.

The system 200 stores the implant design in association with dataidentifying the single group defined for each of the resection cuts(3380). For instance, the system 200 may store, in association with dataidentifying the implant design, data identifying the combination ofgroups corresponding to the implant design. The system 200 further maystore, in association with data identifying the implant design, bonesize measurements and other patient data (e.g., age, gender, ethnicity,weight, height, etc.) that may be useful in determining whether or not apatient matches the implant design. The system 200 may store any type ofdata that enables matching of patient bone data to an implant in thelibrary of implants.

In some implementations, the system 200 may use the clusteringtechniques described throughout this disclosure (e.g., the process 3300)to cluster combined edges. For example, the system 200 may cluster thesides of the implant (e.g., distal, and chamfer cuts) as one group ofclustered segments and then cluster the posterior and anterior tips asseparate entities. Similarly, the system 200 may cluster the sidesmedial and lateral separately, but with each side as an independentmember of the library of “sizes.” The clustered segments of combinededges then may be matched and generally used in the same manner as theindividual clustered segments described throughout this disclosure.

FIG. 34 illustrates a process 3400 for matching patient data to animplant. The process 3400 may be used in performing one or moreoperations related to implant matching based on the segments thatcorrespond to the resection cuts used in fitting the implant on theportion of the bone referenced above with respect to reference numeral2960. The operations of the process 3400 are described generally asbeing performed by the system 200. In some implementations, operationsof the process 3400 may be performed by one or more processors includedin one or more electronic devices.

The system 200, for each segment, compares one or more parameters of thesegment to parameters that are associated with available implant designsand that correspond to the particular resection cut to which the segmentcorresponds (3410) and, based on comparison results, determines whetherthe one or more parameters match an available implant design within athreshold degree (3420). For instance, for a particular resection cut,the system 200 may access parameters stored in association with groupsof clustered segments stored in the library for the particular resectioncut and compare the one or more parameters of a segment for theparticular resection cut to the accessed parameters. Based on thecomparison of the one or more parameters of the segment for theparticular resection cut to the accessed parameters, the system 200determines whether the one or more parameters of a segment for theparticular resection cut match the accessed parameters within athreshold degree.

In some examples, the system 200 may compare a shape of the segment toshapes of outer perimeters of representations stored in the library ofimplant designs. In these examples, based on the comparison of the shapeof the segment to shapes of outer perimeters of representations storedin the library, the system 200 determines whether the shape of thesegment exactly matches a shape of an outer perimeter of arepresentation stored in the library or matches a shape of an outerperimeter of a representation stored in the library within a thresholdtolerance zone (e.g., matches the outer perimeter within two millimetersat all locations).

In some implementations, the system 200 may determine size measurementsof the segment and first compare the determined size measurements tosizes of representations stored in the library. In theseimplementations, the system 200 may, based on the comparison, select asubset of representations within the library that are acceptable for thedetermined size measurements. Although each of the subset ofrepresentations is acceptable for the size of the segment, each of thesubset of representations has a different shape for an outer perimeterof the representation. Accordingly, after selecting the subset, thesystem 200 performs a second comparison to select the representationthat best matches a shape of the segment. In this regard, the system 200compares the one or more parameters of the segment to parametersassociated with each of the subset of representations to assess whethera shape of the segment matches a shape of any of the subset ofrepresentations.

For instance, the system 200 may determine size and/or shapecharacteristics of the segment. The system 200 also may determineposition data for portions of the segment that enables matching torepresentations in the library. The system 200 may determine any type ofparameters that enable matching of the segment to a representation inthe library of implants, including the parameters stored in associationwith representations in the process 3300. The system 200 may use thesegment itself as the one or more parameters.

In some implementations, the system 200 may process each segment anddetermine a matching group of clustered segments for each segment. Inthese implementations, the system 200 may process the segments inparallel, in serial, or in a serial and parallel manner. For instance,in implementations in which the portion of the bone is a distal end of afemur, the system 200 may start with a first segment corresponding tothe distal face of the femur and determine, for the first segment, amatching group of clustered segments that correspond to the distal face.After determining the match for the distal face, the system 200 proceedsto analyze a second segment corresponding to the anterior chamfer of thefemur and a third segment corresponding to the posterior chamfer of thefemur. In analyzing the second segment and the third segment, the system200 only considers groups that are compatible with the matching group ofclustered segments that correspond to the distal face. The system 200determines, for the second segment, a matching group of clusteredsegments that correspond to the anterior chamfer and determines, for thethird segment, a matching group of clustered segments that correspond tothe posterior chamfer, or determines that a match cannot be found. Tothe extent matches for the second and third segments are found, thesystem 200 proceeds to analyze a fourth segment corresponding to theanterior flange of the femur and a fifth segment corresponding to theposterior condyles of the femur. In analyzing the fourth segment and thefifth segment, the system 200 only considers groups that are compatiblewith the matching group of clustered segments that correspond to thedistal face, the matching group of clustered segments that correspond tothe anterior chamfer, and the matching group of clustered segments thatcorrespond to the posterior chamfer. The system 200 determines, for thefourth segment, a matching group of clustered segments that correspondto the anterior flange and determines, for the fifth segment, a matchinggroup of clustered segments that correspond to the posterior condyles,or determines that a match cannot be found. The system 200 thendetermines whether an available implant design matches the segmentsbased on whether all five segments were matched or not. If all fivesegments were matched, the system 200 identifies an available implantdesign designed for the combination of groups matched. If all fivesegments were not matched, the system 200 determines that no availableimplant design matches within a threshold degree.

In implementations in which the segments are processed in parallel, thesystem 200 first determines whether a matching group of clusteredsegments was found for each segment. If a matching group of clusteredsegments was not found for each segment, the system 200 determines thatno available implant design matches within a threshold degree. If amatching group of clustered segments was found for each segment, thesystem 200 determines whether an available implant design has beendefined for the combination of matching groups. For instance, aparticular combination of groups may be rare and, therefore, an implantdesign may not be defined in the library for the particular combinationand, thus, an implant design in the library is not available, eventhough a matching group of clustered segments was found for eachsegment. If an available implant design has been defined for thecombination of matching groups, the system 200 identifies the availableimplant design designed for the combination of groups matched. If anavailable implant design has not been defined for the combination ofmatching groups, the system 200 determines that no available implantdesign matches within a threshold degree.

The system 200, based on determining a match, outputs the availableimplant design as a match of the segments (3430). For instance, thesystem 200 may display the matching implant design to a surgeon (orother medical care provider) for use in an implant procedure. If thesystem 200 determines that multiple implant designs match the segmentswithin the threshold degree, the system 200 may display each of themultiple implant designs to enable a surgeon to select the preferredimplant design for the implant procedure.

In determining a match, the system 200 locates a “best” match that isnot necessarily a “perfect” match, e.g. the system 200 may pick a sizeor several sizes from the implant library that fit “best” while notmeeting all the constraints required to be considered a “perfect” match.Accordingly, the system 200 selects the best match of a discrete sizefrom a pre-existing library matched to fit new patients. The system 200may use the best match as long as the best match fits the new patientwithin a threshold degree.

The system 200, based on determining no match within a threshold degree,determines that a custom implant is needed and outputs a message thatindicates a custom implant is needed (3440). For instance, the system200 may display a message indicating that no match was found in thelibrary of implants. The system 200 also may initiate a process todefine a custom implant for the portion of the bone based on thedetermination that no match exists within the threshold degree.

In some examples, the system 200 constructs clusters of bones inaddition or as an alternative to clusters of contours. In theseexamples, the system 200 may combine the solids of the bones intominimum and maximum bones after the bones have been grouped in clusters.The system 200 then may place the seed implant spline on the contour ofthe ribbon from that composite bone.

FIGS. 35-49 are example interfaces that illustrate an example of using amodular process to select or create a patient specific knee implant. Theexample interfaces may be generated and used in performing the process2900 described above with respect to FIG. 29. FIG. 35 shows arepresentation 3500 of a three-dimensional bone volume intersected witha three-dimensional tolerance volume based on locations of resectionscuts used in fitting an implant on the three-dimensional bone volume.FIG. 36 shows a representation 3600 of the three-dimensional bone volumeand the three-dimensional tolerance volume from FIG. 35 with portions ofthe three-dimensional bone volume outside of the three-dimensionaltolerance volume removed. FIG. 37 shows a representation 3700 of aremaining portion of the three-dimensional bone volume from FIG. 35after intersection with the three-dimensional tolerance volume. FIG. 38shows a representation 3800 of the remaining portion of thethree-dimensional bone volume from FIG. 37 after being modified toaccount for a safe zone for a periphery of an implant. FIG. 39 shows arepresentation 3900 of the modified portion of the three-dimensionalbone volume from FIG. 38 after being modified to account for an implanttolerance zone defined based on sizing of the implant and one or moretolerances for one or more variations related to an implant procedure.FIG. 40 shows a representation 4000 of a bone surface ribbon generatedfrom the volume shown in FIG. 39 and control points for a spline fittedto the bone surface ribbon.

FIGS. 41-48 illustrate segments of bone data generated from the bonedata shown in FIGS. 39 and 40. FIG. 41 shows a representation 4100 ofthe portion of the bone data shown in FIG. 39 that corresponds to theanterior flange. FIG. 42 shows a representation 4200 of the portion ofthe bone surface ribbon and control points shown in FIG. 40 thatcorresponds to the anterior flange. FIG. 43 shows a representation 4300of the portion of the bone data shown in FIG. 39 that corresponds to theanterior chamfer cut. FIG. 44 shows a representation 4400 of the portionof the bone surface ribbon and control points shown in FIG. 40 thatcorresponds to the anterior chamfer cut. FIG. 45 shows a representation4500 of the portion of the bone data shown in FIG. 39 that correspondsto the distal and posterior chamfer cuts. FIG. 46 shows a representation4600 of the portion of the bone surface ribbon and control points shownin FIG. 40 that corresponds to the distal and posterior chamfer cuts.FIG. 47 shows a representation 4700 of the portion of the bone datashown in FIG. 39 that corresponds to the posterior condyles. FIG. 48shows a representation 4800 of the portion of the bone surface ribbonand control points shown in FIG. 40 that corresponds to the posteriorcondyles.

FIG. 49 shows a representation 4900 of a patient specific implant basedon the bone sections shown in FIGS. 41-48. The patient specific implantmay be an implant selected from a library of available implant designsusing the techniques described above with respect to FIG. 34. Thepatient specific implant may be a custom implant designed based on thebone sections shown in FIGS. 41-48.

FIG. 50 illustrates an example of a generic computer system 2000. Thesystem 2000 can be used for the operations described in association withthe approach 100 and the processes 300, 400, 700, 1600, 1700, 2900,3300, and 3400, according to some implementations. The system 2000 maybe included in the system 200.

The system 2000 includes a processor 2010, a memory 2020, a storagedevice 2030, and an input/output device 2040. Each of the components2010, 2020, 2030, and 2040 are interconnected using a system bus 2050.The processor 2010 is capable of processing instructions for executionwithin the system 2000. In one implementation, the processor 2010 is asingle-threaded processor. In another implementation, the processor 2010is a multi-threaded processor. The processor 2010 is capable ofprocessing instructions stored in the memory 2020 or on the storagedevice 2030 to display graphical information for a user interface on theinput/output device 2040.

The memory 2020 stores information within the system 2000. In oneimplementation, the memory 2020 is a computer-readable medium. In oneimplementation, the memory 2020 is a volatile memory unit. In anotherimplementation, the memory 2020 is a non-volatile memory unit.

The storage device 2030 is capable of providing mass storage for thesystem 1000. In one implementation, the storage device 2030 is acomputer-readable medium. In various different implementations, thestorage device 2030 may be a floppy disk device, a hard disk device, anoptical disk device, or a tape device.

The input/output device 2040 provides input/output operations for thesystem 1000. In one implementation, the input/output device 2040includes a keyboard and/or pointing device. In another implementation,the input/output device 2040 includes a display unit for displayinggraphical user interfaces.

The features described can be implemented in digital electroniccircuitry, or in computer hardware, firmware, software, or incombinations of them. The apparatus can be implemented in a computerprogram product tangibly embodied in an information carrier, e.g., in amachine-readable storage device, for execution by a programmableprocessor; and method steps can be performed by a programmable processorexecuting a program of instructions to perform functions of thedescribed implementations by operating on input data and generatingoutput. The described features can be implemented advantageously in oneor more computer programs that are executable on a programmable systemincluding at least one programmable processor coupled to receive dataand instructions from, and to transmit data and instructions to, a datastorage system, at least one input device, and at least one outputdevice. A computer program is a set of instructions that can be used,directly or indirectly, in a computer to perform a certain activity orbring about a certain result. A computer program can be written in anyform of programming language, including compiled or interpretedlanguages, and it can be deployed in any form, including as astand-alone program or as a module, component, subroutine, or other unitsuitable for use in a computing environment.

Suitable processors for the execution of a program of instructionsinclude, by way of example, both general and special purposemicroprocessors, and the sole processor or one of multiple processors ofany kind of computer. Generally, a processor will receive instructionsand data from a read-only memory or a random access memory or both. Theelements of a computer are a processor for executing instructions andone or more memories for storing instructions and data. Generally, acomputer will also include, or be operatively coupled to communicatewith, one or more mass storage devices for storing data files; suchdevices include magnetic disks, such as internal hard disks andremovable disks; magneto-optical disks; and optical disks. Storagedevices suitable for tangibly embodying computer program instructionsand data include all forms of non-volatile memory, including by way ofexample semiconductor memory devices, such as EPROM, EEPROM, and flashmemory devices; magnetic disks such as internal hard disks and removabledisks; magneto-optical disks; and CD-ROM and DVD-ROM disks. Theprocessor and the memory can be supplemented by, or incorporated in,ASICs (application-specific integrated circuits).

To provide for interaction with a user, the features can be implementedon a computer having a display device such as a CRT (cathode ray tube)or LCD (liquid crystal display) monitor for displaying information tothe user and a keyboard and a pointing device such as a mouse or atrackball by which the user can provide input to the computer.

The features can be implemented in a computer system that includes aback-end component, such as a data server, or that includes a middlewarecomponent, such as an application server or an Internet server, or thatincludes a front-end component, such as a client computer having agraphical user interface or an Internet browser, or any combination ofthem. The components of the system can be connected by any form ormedium of digital data communication such as a communication network.Examples of communication networks include, e.g., a LAN, a WAN, and thecomputers and networks forming the Internet.

The computer system can include clients and servers. A client and serverare generally remote from each other and typically interact through anetwork, such as the described one. The relationship of client andserver arises by virtue of computer programs running on the respectivecomputers and having a client-server relationship to each other.

The tangible computer-readable mediums described throughout thisdisclosure may be referred to as non-transitory computer-readablemediums. Non-transitory computer-readable mediums may include any typeof hardware storage device and the term non-transitory may be used todistinguish from intangible information carriers, such as propagatingsignals.

There is also provided a method for locating an implant. The methodincludes the steps of: preparing a distal end of a femur; locating amaximum distal width of the distal end; placing an instrument on theprepared femur, moving the instrument in a medial-lateral direction toobtain equal perimeter offsets; pinning the instrument; and creating atleast one lug hole in the distal end of the femur using the instrument.The instrument includes a distal cut surface portion; an anteriorchamfer portion connected to the distal cut surface portion; anteriorflange portion connected to the anterior chamfer portion; a posteriorchamfer portion connected to the distal cut surface portion; and atleast one paddle connected to the posterior chamfer portion. The step ofcreating at least one lug uses a drill, a reamer or a punch. In someembodiments, the method includes the steps of removing the instrumentand implanting a knee prosthesis.

There is provided a method for manufacturing a positioner instrument.The method includes the steps of: obtaining image data; generating aribbon using the image data; generating a spline using the ribbon;generating offset distances for at least one lug location; importing thespline into an instrument CAD model; placing the offset distances in theinstrument CAD model; and outputting the instrument CAD model to a SLAfile.

As various modifications could be made to the exemplary embodiments, asdescribed above with reference to the corresponding illustrations,without departing from the scope of the invention, it is intended thatall matter contained in the foregoing description and shown in theaccompanying drawings shall be interpreted as illustrative rather thanlimiting. Thus, the breadth and scope of the invention should not belimited by any of the above-described exemplary embodiments, but shouldbe defined only in accordance with the claims and their equivalents.

What is claimed is:
 1. A system comprising: at least one processor; andat least one computer-readable medium coupled to the at least oneprocessor having stored thereon instructions which, when executed by theat least one processor, causes the at least one processor to performoperations comprising: accessing a three-dimensional model of at least aportion of a bone; determining a three-dimensional bone volume based onthe three-dimensional model of the portion of the bone and resectioncuts used in fitting an implant on the portion of the bone; determininga three-dimensional outline representation of at least a portion of anouter surface of a periphery of the three-dimensional bone volume;converting the three-dimensional outline representation into atwo-dimensional outline representation of the portion of the outersurface of the periphery of the three-dimensional bone volume;segmenting the two-dimensional outline representation into segments thatcorrespond to the resection cuts used in fitting the implant on theportion of the bone, each segment corresponding to a particularresection cut and including data representing an outline of the bone atthe particular resection cut; and performing one or more operationsrelated to implant matching based on the segments that correspond to theresection cuts used in fitting the implant on the portion of the bone.2. The system of claim 1, wherein performing one or more operationsrelated to implant matching comprises: for each segment, storing thesegment in a database with sample segments determined for the particularresection cut on other bone portions that correspond to the portion ofthe bone; and for each resection cut: analyzing characteristics of thesegments stored in the database for the resection cut, based on theanalysis, clustering the segments stored in the database for theresection cut into multiple groups that each includes segments havingsimilar characteristics, and defining a representation of clusteredsegments for each of the multiple groups.
 3. The system of claim 2,wherein performing one or more operations related to implant matchingcomprises: for each segment, comparing the segment to representations ofclustered segments for each of the multiple groups that correspond tothe particular resection cut to which the segment corresponds; based oncomparison results, determining matching groups that include a group foreach resection cut; and selecting an implant design based on thematching groups.
 4. The system of claim 2, wherein performing one ormore operations related to implant matching comprises: accessingrepresentations of clustered segments that include a representation ofclustered segments for a single group defined for each of the resectioncuts; reassembling the accessed representations into a two-dimensionaloutline representation of the portion of the bone; generating an implantdesign based on the reassembled two-dimensional outline representationof the portion of the bone; and storing the implant design inassociation with data identifying the single group defined for each ofthe resection cuts.
 5. The system of claim 1, wherein performing one ormore operations related to implant matching comprises: for each segment,comparing one or more parameters of the segment to parameters that areassociated with available implant designs and that correspond to theparticular resection cut to which the segment corresponds; based oncomparison results, determining a match for an available implant design;and based on the determination of the match for the available implantdesign, outputting the available implant design.
 6. The system of claim1, wherein performing one or more operations related to implant matchingcomprises designing a custom implant based on the segments thatcorrespond to the resection cuts used in fitting the implant on theportion of the bone.
 7. The system of claim 1, wherein accessing thethree-dimensional model of at least the portion of the bone comprises:accessing one or more images of the portion of the bone; and generatingthe three-dimensional model of the portion of the bone based on the oneor more images of the portion of the bone.
 8. The system of claim 1:wherein determining the three-dimensional bone volume based on thethree-dimensional model of the portion of the bone and resection cutsused in fitting an implant on the portion of the bone comprises:defining a three-dimensional solution volume based on resection cutsused in fitting an implant on the portion of the bone; and intersectingthe three-dimensional model of the portion of the bone with thethree-dimensional solution volume to produce a resultant bone volumerepresented in three dimensions; and wherein determining thethree-dimensional outline representation of at least the portion of theouter surface of the periphery of the three-dimensional bone volumecomprises determining an outline representation of at least a portion ofan outer surface of a periphery of the resultant bone volume.
 9. Thesystem of claim 8: wherein defining the three-dimensional solutionvolume based on resection cuts used in fitting the implant on theportion of the bone comprises defining a three-dimensional tolerancevolume based on one or more tolerances for one or more variationsrelated to an implant procedure for placing the implant on the portionof the bone; and wherein intersecting the three-dimensional model of theportion of the bone with the three-dimensional solution volume toproduce the resultant bone volume represented in three dimensionscomprises intersecting the three-dimensional model of the portion of thebone with the three-dimensional tolerance volume to produce theresultant bone volume represented in three dimensions.
 10. The system ofclaim 9, wherein converting the three-dimensional outline representationinto the two-dimensional outline representation of the portion of theouter surface of the periphery of the three-dimensional bone volumecomprises converting the three-dimensional outline representation into atwo-dimensional outline representation that has a thickness to accountfor the one or more tolerances for the one or more variations related tothe implant procedure for placing the implant on the portion of thebone.
 11. The system of claim 10, wherein defining the three-dimensionaltolerance volume based on one or more tolerances for one or morevariations related to an implant procedure for placing the implant onthe portion of the bone comprises defining the three-dimensionaltolerance volume based on at least one of a tolerance related tovariations in surgical technique in performing the implant procedure, atolerance related to variations in medical instrumentation used inperforming the implant procedure, a tolerance related to variations inmanufacturing the implant used in the implant procedure, a tolerancerelated to variations in anatomy of similar bones across patients, atolerance related to variations in medical imaging used in generatingthe three-dimensional model of the portion of the bone, and a tolerancerelated to variations in file conversion used in generating thethree-dimensional model of the portion of the bone.
 12. The system ofclaim 10, wherein defining the three-dimensional tolerance volume basedon one or more tolerances for one or more variations related to animplant procedure for placing the implant on the portion of the bonecomprises: identifying the one or more tolerances for the one or morevariations related to the implant procedure; determining one or moremeasurements that account for the one or more tolerances identified;determining locations of resection cuts used in fitting the implant onthe portion of the bone; and defining the three-dimensional tolerancevolume based on the locations of the resection cuts and the one or moremeasurements that account for the one or more tolerances identified. 13.The system of claim 1: wherein determining the three-dimensional outlinerepresentation of at least the portion of the outer surface of theperiphery of the three-dimensional bone volume comprises creating a bonesurface ribbon from the outer surface of the periphery of thethree-dimensional bone volume; and wherein converting thethree-dimensional outline representation into the two-dimensionaloutline representation of the portion of the outer surface of theperiphery of the three-dimensional bone volume comprises converting thebone surface ribbon into the two-dimensional outline representation ofthe portion of the outer surface of the periphery of thethree-dimensional bone volume.
 14. The system of claim 13: whereindetermining the three-dimensional outline representation of at least theportion of the outer surface of the periphery of the three-dimensionalbone volume comprises fitting a curve to the bone surface ribbon; andwherein converting the bone surface ribbon into the two-dimensionaloutline representation of the portion of the outer surface of theperiphery of the three-dimensional bone volume comprises converting thecurve fitted to the bone surface ribbon into the two-dimensional outlinerepresentation of the portion of the outer surface of the periphery ofthe three-dimensional bone volume.
 15. The system of claim 1, whereinconverting the three-dimensional outline representation into thetwo-dimensional outline representation of the portion of the outersurface of the periphery of the three-dimensional bone volume comprisesconverting the three-dimensional outline representation into atwo-dimensional outline representation that has a thickness to accountfor one or more tolerances for one or more variations related to animplant procedure for placing the implant on the portion of the bone.16. The system of claim 1, wherein converting the three-dimensionaloutline representation into the two-dimensional outline representationof the portion of the outer surface of the periphery of thethree-dimensional bone volume comprises offsetting the two-dimensionaloutline representation to reduce the likelihood of overhang of theimplant on the portion of the bone.
 17. The system of claim 1: whereinaccessing the three-dimensional model of at least the portion of thebone comprises accessing a three-dimensional model of a distal end of afemur; and wherein segmenting the two-dimensional outline representationinto segments that correspond to the resection cuts used in fitting theimplant on the portion of the bone comprises segmenting thetwo-dimensional outline representation into a first segment thatcorresponds to a distal face of the distal end of the femur, a secondsegment that corresponds to an anterior chamfer of the distal end of thefemur, a third segment that corresponds to a posterior chamfer of thedistal end of the femur, a fourth segment that corresponds to ananterior flange of the distal end of the femur, and a fifth segment thatcorresponds to posterior condyles of the distal end of the femur. 18.The system of claim 17, wherein performing one or more operationsrelated to implant matching comprises: determining a first match for thefirst segment that corresponds to the distal face of the distal end ofthe femur to a representation of clustered segments for a distal faceresection cut; after determining the first match for the first segment:determining a second match for the second segment that corresponds tothe anterior chamfer of the distal end of the femur to a representationof clustered segments for an anterior chamfer resection cut, anddetermining a third match for the third segment that corresponds to theposterior chamfer of the distal end of the femur to a representation ofclustered segments for a posterior chamfer resection cut; afterdetermining the second match for the second segment and determining thethird match for the third segment: determining a fourth match for thefourth segment that corresponds to the anterior flange of the distal endof the femur to a representation of clustered segments for an anteriorflange resection cut, and determining a fifth match for the fifthsegment that corresponds to the posterior condyles of the distal end ofthe femur to a representation of clustered segments for a posteriorcondyles resection cut; and selecting an available implant design basedon the first match for the first segment, the second match for thesecond segment, the third match for the third segment, the fourth matchfor the fourth segment, and the fifth match for the fifth segment.
 19. Amethod comprising: accessing a three-dimensional model of at least aportion of a bone; determining a three-dimensional bone volume based onthe three-dimensional model of the portion of the bone and resectioncuts used in fitting an implant on the portion of the bone; determininga three-dimensional outline representation of at least a portion of anouter surface of a periphery of the three-dimensional bone volume;converting, by at least one processor, the three-dimensional outlinerepresentation into a two-dimensional outline representation of theportion of the outer surface of the periphery of the three-dimensionalbone volume; segmenting the two-dimensional outline representation intosegments that correspond to the resection cuts used in fitting theimplant on the portion of the bone, each segment corresponding to aparticular resection cut and including data representing an outline ofthe bone at the particular resection cut; and performing one or moreoperations related to implant matching based on the segments thatcorrespond to the resection cuts used in fitting the implant on theportion of the bone.
 20. At least one computer-readable storage mediumencoded with executable instructions that, when executed by at least oneprocessor, cause the at least one processor to perform operationscomprising: accessing a three-dimensional model of at least a portion ofa bone; determining a three-dimensional bone volume based on thethree-dimensional model of the portion of the bone and resection cutsused in fitting an implant on the portion of the bone; determining athree-dimensional outline representation of at least a portion of anouter surface of a periphery of the three-dimensional bone volume;converting the three-dimensional outline representation into atwo-dimensional outline representation of the portion of the outersurface of the periphery of the three-dimensional bone volume;segmenting the two-dimensional outline representation into segments thatcorrespond to the resection cuts used in fitting the implant on theportion of the bone, each segment corresponding to a particularresection cut and including data representing an outline of the bone atthe particular resection cut; and performing one or more operationsrelated to implant matching based on the segments that correspond to theresection cuts used in fitting the implant on the portion of the bone.